Congress certified the election of President-elect Joseph R. Biden Jr. early Thursday, hours after loyalists urged on by President Trump stormed and occupied the Capitol, disrupting the final electoral count in a shocking display of violence that shook the core of American democracy.

Mr. Trump, who spent months stoking the anger of his supporters with false claims that the election was stolen and who refused to condemn the violent protests on Wednesday, said early Thursday that there would be an orderly presidential transition this month.

“Even though I totally disagree with the outcome of the election, and the facts bear me out, nevertheless there will be an orderly transition on January 20th,” he said in a statement.

The statement, which had to be issued through surrogates since Mr. Trump’s Twitter account was suspended, came moments after Vice President Mike Pence affirmed Mr. Biden as the winner of the presidential election shortly before 4 a.m. after the final electoral votes were tallied in a joint session of Congress.

There was no parallel in modern American history, with insurgents acting in the president’s name vandalizing Speaker Nancy Pelosi’s office, smashing windows, looting art and briefly taking control of the Senate chamber, where they took turns posing for photographs with fists up on the dais where Mr. Pence had just been presiding.

Mr. Biden, speaking as the scenes of destruction in the halls of Congress left lawmakers from both parties horrified, blamed Mr. Trump for fomenting the insurrection.

“At their best, the words of a president can inspire. At their worst, they can incite,” Mr. Biden said.

Allies around the world, accustomed to the chaos that has marked Mr. Trump’s tenure, struggled to find words to describe what they were witnessing.

“These pictures made me angry and sad,” Chancellor Angela Merkel of Germany said.

In Russia, by contrast, the violence fit neatly into the Kremlin’s narrative of a crumbling American democracy. The Kremlin released no official comment, but state television offered extensive late-night coverage of the attack on the Capitol, with the footage of the violence set to dramatic, orchestral music.

The upheaval unfolded on a day when Democrats secured a stunning pair of victories in runoff elections in Georgia, winning effective control of the Senate and the levers of power in Washington.

The siege at the Capitol was the climax of a weekslong campaign by Mr. Trump, filled with baseless claims of fraud and outright lies, to try to overturn a democratically decided election that he lost.

By the time the Senate reconvened late Wednesday, hours after lawmakers had been evacuated from a Capitol overrun by a mob carrying pro-Trump paraphernalia, one of the nation’s most polarizing moments had yielded an unexpected window of solidarity. Republicans and Democrats locked arms to denounce the violence and express their determination to carry out what they called a constitutionally sacrosanct function.

“To those who wreaked havoc in our Capitol today, you did not win,” Mr. Pence said in a sharp break from Mr. Trump, who had posted messages condoning the mob’s actions. “Violence never wins. Freedom wins. And this is still the people’s house.”

Senator Mitch McConnell, Republican of Kentucky and the majority leader, said the “failed insurrection” had only clarified Congress’s purpose.

“They tried to disrupt our democracy,” he said. “They failed.”

After the vote was certified early Thursday, Barry C. Black, the Senate chaplain, said a prayer in the chamber in an emotional close to a chaotic day in which a woman was fatally shot inside the Capitol.

“These tragedies have reminded us that words matter and that the power of life and death is in the tongue,” he said. “We deplore the desecration of the United States Capitol building, the shedding of innocent blood, the loss of life, and the quagmire of dysfunction that threaten our democracy.”

Congress rejected an attempt from Republicans to overturn the will of Pennsylvania voters early Thursday, effectively ending a final attempt from insurgents to turn a loss for President Trump in the state into a win.

The House rejected the challenge by a vote of 282 to 138, after a long debate dragged past 3 a.m. in Washington. A scuffle almost broke out on the chamber floor after Representative Conor Lamb, Democrat of Pennsylvania, delivered a particularly fiery speech in condemnation of the Republican objections.

“That attack today, it didn’t materialize out of nowhere,” Mr. Lamb said. “It was inspired by lies, the same lies you’re hearing in this room tonight, and the members who are repeating those lies should be ashamed of themselves.”

By a vote of 92 to 7, the Senate turned back the Pennsylvania challenge shortly before 1 a.m., as the number of objections to the counting of Electoral College votes dwindled after the mob’s brazen effort to keep President Trump in office, despite his decisive election loss in November.

Those senators voting against the results of the presidential election in Pennsylvania were: Josh Hawley of Missouri, Ted Cruz of Texas, Tommy Tuberville of Alabama, Cindy Hyde-Smith of Mississippi, Roger Marshall of Kansas, Cynthia Lummis of Wyoming and Rick Scott of Florida.

As most Republicans and all Democrats rejected the attempt, Senator Mike Lee, Republican of Utah, forcefully turned back the plot, registering his vote as “hell no.”

Earlier in the evening, lawmakers rejected an attempt to overturn the Arizona electoral slate. The House blocked the attempt with a 303-to-121 vote while the Senate offered a sharper rebuke with a 93-to-6 vote.

After debating the merits of subverting the majority of Arizona voters, lawmakers sped through the certification for several states after at least four Republican lawmakers, including Senator Kelly Loeffler of Georgia, said they had changed their minds and would vote to uphold the Electoral College results after having previously said that they would object to them.

Those voting against the results of the election in Arizona were: Mr. Hawley, Mr. Cruz, Mr. Tuberville, Ms. Hyde-Smith, Mr. Marshall and John Kennedy of Louisiana.

The move by Ms. Loeffler, who lost a special election in Georgia and failed to retain her Senate seat, amounted to one of her last acts in the upper chamber, and she announced her reversal during remarks on the Senate floor after the debate resumed late Wednesday.

Ms. Loeffler’s remarks came after Representative Cathy McMorris Rodgers of Washington and Senator Steve Daines of Montana condemned the actions of Trump loyalists who broke into the Capitol earlier on Wednesday and said they would no longer back an effort by some of their Republican colleagues to throw out the election results.

Ms. McMorris Rodgers’s remarks were particularly pointed.

“Thugs assaulted Capitol Police officers, breached and defaced our Capitol building, put people’s lives in danger and disregarded the values we hold dear as Americans,” Ms. McMorris Rodgers said in a statement, which she released a day after declaring she would object to the vote counts. “To anyone involved, shame on you.”

“What we have seen today is unlawful and unacceptable,” she added. “I have decided I will vote to uphold the Electoral College results, and I encourage Donald Trump to condemn and put an end to this madness.”

Shortly after Ms. McMorris Rodgers announced her decision, Mr. Daines followed suit, saying he, too, would certify electoral votes after having previously signed onto a letter saying he and other Republican senators “intend to vote on Jan. 6 to reject the electors” from some states.

“Today is a sad day for our country. The destruction and violence we saw at our Capitol today is an assault on our democracy, our Constitution and the rule of law, and must not be tolerated,” he said in his new statement Wednesday night.

Mick Mulvaney, President Trump’s former acting chief of staff, resigned his post as special envoy to Northern Ireland on Wednesday night in response to the president’s encouragement of a mob that rioted at the Capitol complex earlier in the day. The president’s deputy national security adviser, Matt Pottinger, resigned as well, a person familiar with the events said on Thursday.

In an interview with CNBC on Thursday morning, Mr. Mulvaney, who was pushed out as acting chief of staff in March, said he called Secretary of State Mike Pompeo the night before to tell him.

“I can’t stay here, not after yesterday,” said Mr. Mulvaney, tying his resignation to the violence at the Capitol. “You can’t look at that yesterday and think ‘I want to be part of that’ in any way, shape or form.”Mr. Pottinger was one of the key advocates inside the White House for a more robust response to the coronavirus early last year and was ridiculed by co-workers for wearing a mask to work, according to a piece in The New Yorker late last month.

Other officials are considering resigning in response to Wednesday’s siege at the Capitol as well. But one of those who had been said to be considering leaving, the national security adviser, Robert C. O’Brien, plans to stay, in part out of concern about leaving no one in the government at its tumultuous end, another person familiar with events said.

Mr. Mulvaney on Thursday praised administration officials who defended Vice President Mike Pence, who certified the Electoral College vote despite Mr. Trump pressuring him to overturn the results of the election.

Mr. Mulvaney said he anticipated there would be more resignations and praised the small group of people who quit on Wednesday.

“Those who choose to stay, and I have talked with some of them, are choosing to stay because they’re worried the president might put someone worse in,” said Mr. Mulvaney, who once publicly acknowledged and defended the president’s move to suspend $391 million in aid to Ukraine in exchange for investigations into his political rivals, a scheme at the heart of Mr. Trump’s impeachment.

In the hours after Mr. Trump took to social media on Wednesday to openly condone the violence at the Capitol, he found himself increasingly isolated as White House officials began submitting their resignations, with more expected to follow suit.

Stephanie Grisham, the former White House press secretary who served as the chief of staff to Melania Trump, the first lady, submitted her resignation after the violent protests. Ms. Grisham has worked for the Trumps since the 2016 campaign and is one of their longest-serving aides.

Rickie Niceta, the White House social secretary, also said she was resigning, according to an administration official familiar with her plans who was not authorized to speak publicly. And Sarah Matthews, a deputy White House press secretary, also submitted her resignation, saying in a statement that she was “deeply disturbed by what I saw today.”

The actions of law enforcement officials before, during and after a violent breach of the Capitol on Tuesday by a pro-Trump mob were coming into question as images emerged of officers gently escorting rioters to their freedom — and a video showing officers pushing aside barricades used to keep the mob from entering the complex.

The law enforcement agencies responsible for protecting the complex, a patchwork of federal and local agencies led by the 2,000-member Capitol Police force, are already facing scrutiny over their inability to counter the violence despite weeks of none-too-secret planning by the attackers on social media sites like Gab and Parler.

The Capitol Police, which is shielded from the transparency requirements of other federal agencies by law, did not respond to requests for comment on Tuesday, nor have they issued any statements about the incident.

Representative Maxine Waters, a California Democrat, said on Twitter late Tuesday: “We must investigate the security breach at the Capitol today. I warned our Caucus and had an hour long conversation with the Chief of Police 4days ago. He assured me the terrorists would not be allowed on the plaza & Capitol secured.”

When debate over certification of the presidential election resumed amid shattered glass, lawmakers from both parties praised the heroism of the officers who battled with violent protesters.

But many in the mob, which numbered in the hundreds, appeared to act with the abandon of lawbreakers confident they would not be held accountable.

Some gleefully snatched and smashed cameras from journalists, others smiled without masks for selfies, and one Richard Barnett, 60, from Gravette, Ark., amiably recounted his invasion of Speaker Nancy Pelosi’s personal office to a reporter after posing for a picture with his feet on her desk.

“Why on earth is this man not under arrest and in prison?” Ben Rhodes, a former speechwriter for President Obama, asked on Twitter.

The contrast between the treatment of the mostly white pro-Trump mob and the massive show of force to counter more peaceful and racially diverse protests against police violence last summer was striking to many.

“It was strange, because it was almost like there was this call to not use force,” Representative Cori Bush, a Democrat from St. Louis, said in an interview with MSNBC shortly after the attack.

Ms. Bush said that the rioters “would have been shot” if they were Black, adding the treatment reflected “white privilege.”

Law enforcement officials told lawmakers on Tuesday that their main priority was to clear the complex quickly, rather than make arrests, so that legislative activity could resume as soon as possible.

As of 9:30 p.m. Tuesday, the last accounting offered by law enforcement agencies, at least 52 people were arrested, including five on weapons charges and at least 26 on the grounds of the Capitol. Most of the arrests were for violating the 6 p.m. curfew, he said, adding that the police would circulate pictures of those sought for breaching the Capitol building.

In addition, pipe bombs were found at the headquarters of both the Republican and the Democratic National Committees and a cooler containing a long gun and Molotov cocktails was discovered on the Capitol grounds, Washington D.C. police officials said.

On Wednesday morning, the F.B.I. posted a web page for tips about individuals involved in the violence, and details of new attacks that might be in the works — allowing citizens to download digital images of people involved.

The Trump supporters pressed through police barricades, broke windows and battered their way with metal poles through entrances to the Capitol. Then, stunningly, they breached the “People’s House” itself, forcing masked police officers to draw their guns to keep the insurgents off the chamber floor.

“I thought we’d have to fight our way out,” said Representative Jason Crow, Democrat of Colorado and a former Army Ranger in Iraq, who found himself captive in the House chamber.

What unfolded at that point, at times on national television, was a tableau of violence and mayhem that shocked the nation, one of the most severe intrusions of the Capitol since the British invaded during the War of 1812 and burned it down.

An armed standoff ensued in the House chamber, with police officers drawing their weapons. A pro-Trump extremist casually monkeyed around at the dais of the Senate. Intruders in Speaker Nancy Pelosi’s suite overturned desks and smashed photos. Others ripped artwork in Senate hideaway offices.

“This is what the president has caused today, this insurrection,” Senator Mitt Romney, Republican of Utah, said as he and other senators were hustled off to a secure location.

Some protesters gawked at the grand and storied building they had flooded while others looked at it with contempt.

“I don’t trust any of these people,” said Eric Martin, 49, a woodworker from Charleston, S.C., as he marveled at the opulence of the Capitol and helped a friend wash pepper spray from his eyes. “Absolute power corrupts absolutely.”

But if some only stared at the Capitol, others resorted to violence. A woman inside the building was shot and later died, the District of Columbia police said, and multiple officers were injured. Two explosive devices were found around noon near the headquarters of the Republican National Committee, then destroyed by a bomb squad. And the federal authorities arrested a 70-year-old man from Alabama near the Capitol in possession of a firearm and materials to make several Molotov cocktails.

By Wednesday evening, the scene outside the Capitol had calmed, after Capitol Police, supplemented by F.B.I. agents and Department of Homeland Security officers with members of the National Guard on their way, squeezed pro-Trump extremists from every corner of the building to the majestic Rotunda, then persuaded them to leave.

Even after a mob of Trump supporters swarmed and entered the Capitol on Wednesday, a handful of Republican senators and more than 100 Republican representatives stood by their decisions to vote against certifying the results of the presidential election.

Congress certified the election of Joseph R. Biden Jr. early Thursday, ending attempts to overturn the results in two states. Senators Josh Hawley of Missouri, Ted Cruz of Texas, Tommy Tuberville of Alabama, Cindy Hyde-Smith of Mississippi, Roger Marshall of Kansas and John Kennedy of Louisiana voted to overturn the results in Arizona, while 93 senators voted against. Mr. Hawley, Mr. Cruz, Mr. Tuberville, Ms. Hyde-Smith, Mr. Marshall and Senators Cynthia Lummis of Wyoming and Rick Scott of Florida voted to overturn the results in Pennsylvania, while 92 voted against it.

The House rejected the Arizona challenge by a vote of 303 to 121 and rejected the Pennsylvania challenge by a vote of 282 to 138.

At least four Republican senators who had pledged to back the effort to throw out the election results reversed course after Wednesday’s siege at the Capitol, saying the lawlessness and chaos had caused them to changed their minds.

Those included Senator Marsha Blackburn of Tennessee and Senator Kelly Loeffler of Georgia, who, after losing a special election on Tuesday, announced her reversal on the Senate floor late Wednesday. “The events that have transpired today have forced me to reconsider, and I cannot now, in good conscience, object,” she said.

Senator James Lankford, Republican of Oklahoma, changed his position late Wednesday, releasing a joint statement with Senator Steve Daines of Montana that called on “the entire Congress to come together and vote to certify the election results.”

Representative Cathy McMorris Rodgers of Washington also condemned the actions of the mob of Trump loyalists and said she would no longer vote against the vote certifications.

“Thugs assaulted Capitol Police officers, breached and defaced our Capitol building, put people’s lives in danger and disregarded the values we hold dear as Americans,” Ms. McMorris Rodgers said in a statement, which she released a day after declaring she would object to the vote counts. “To anyone involved, shame on you.”

Congressmen including Representative Lance Gooden, Republican of Texas, said the violence did not change his mind.

“While I’m disgusted with what I saw today, mob riots don’t suddenly make this election secure. YES, of course, I’m still objecting,” he said in a tweet.

Ms. Hyde-Smith of Mississippi said that she voted against the certification of the election because the people she represent do not believe the presidential election was constitutional. “I cannot in good conscience support certification,” she said in a statement on Wednesday.

Chancellor Angela Merkel of Germany on Thursday condemned the mob violence at the U.S. Capitol and blamed the chaos on the rhetoric of President Trump, as leaders around the world expressed concern about the health of American democracy.

Ms. Merkel said she deeply regretted that Mr. Trump had not accepted his defeat in the election and again on Wednesday failed to accept its outcome. “He stoked uncertainties about the election outcome, and that created an atmosphere that made the events of last night possible,” she said.

Ms. Merkel, who addressed a joint session of Congress during a visit to Washington in 2009, said it was “tragic” that people lost their lives during Wednesday’s violence but that it was a sign of “hope” that Congress worked through the night. A woman was fatally shot inside the Capitol and three other deaths were reported nearby, the police said.

Ms. Merkel’s comments mirrored a deep-seated faith in the strength of democracy in the United States that is held by many in Europe.

President Emmanuel Macron of France, in a formal address recalling longstanding ties between his country and the United States, said the chaos in Washington did not reflect the America he knew.

“We believe in the strength of our democracies,” Mr. Macron said. “We believe in the strength of American democracy.”

Le Monde, one of France’s leading newspapers, said in an editorial on Thursday that the violence in Washington amounted to a “day of shame.”

In the first government response from Russia, the spokeswoman for the country’s foreign ministry, Maria Zakharova, said, “We once again point out that the electoral system in the United States is archaic and doesn’t meet modern standards of democracy, creating the possibility for multiple violations and the American media have become instruments of political struggle.”

Ms. Zakharova said she hoped the “friendly people of America will with dignity get through this dramatic period in their own history.”

Russian politicians and political analysts were quick to point out that the attack on the Capitol would send immediate ripples through one cornerstone of U.S. foreign policy: support for pro-Western protesters in the street politics of Eastern Europe and the former Soviet Union.

“Color revolutions just lost a serious argument in their favor,” Konstantin F. Zatulin, deputy chairman of a committee in Russia’s Parliament on relations with former Soviet states, said in an interview, referring to American-supported popular uprisings in countries including Georgia, Serbia and Ukraine over the past two decades.

In Asia, much of which was asleep while U.S. lawmakers were being evacuated from the Capitol, the unsettling scenes from Washington greeted those who were starting their day.

In China, a spokeswoman for the Ministry of Foreign Affairs, Hua Chunying, pointedly referred to American expressions of support for the huge protests that took place in Hong Kong, which at one point included the takeover of the legislature in 2019.

“You may still remember that at the time, American officials, congressmen and some media — what phrases did they use for Hong Kong?” she said in Beijing on Thursday. “What phrases are they using for America now?”

Prime Minister Jacinda Ardern of New Zealand said she and her country were “devastated” by the events in the United States, but she expressed confidence that democracy would ultimately prevail.

“The right of people to exercise a vote, have their voice heard and then have that decision upheld peacefully should never be undone by a mob,” she wrote on Twitter.

Charles Santiago, an opposition lawmaker in Malaysia, said that Mr. Trump had joined other world leaders “in subverting democracy and the will of the people.” He cited Prime Minister Hun Sen of Cambodia and President Rodrigo Duterte of the Philippines.

“The U.S. has lost its moral authority to preach democracy and human rights to other countries,” he said. “It has become part of the problem.”

Even as scores of President Trump’s usually unfailing loyalists condemned him for failing to call off the swarm of lawless demonstrators storming and ransacking the Capitol, many of his most vocal and visible defenders still could not bring themselves to fault the president for the surreal and frightening attack carried out in his name.

They played down the violence as acts of desperation by people who felt lied to by the media and ignored by their elected representatives. They deflected with false equivalencies about the Democratic Party’s embrace of the Black Lives Matter movement.

Some even tried to dispute the fact that Trump supporters were actually the true perpetrators, suggesting that far-left activists had infiltrated the crowd and were posing as fans of Mr. Trump.

“To any insincere, fake DC ‘patriots’ used as PLANTS — you will be found out,” wrote Sarah Palin, the Republican Party’s vice-presidential nominee in 2008, who demanded that the media look into the identities of the people who smashed their way into the Capitol.

Responses like these — full of whataboutism, misdirection and denial — sounded almost like typical fare coming from stalwart defenders of a president who considers admitting fault to be a sign of weakness. That they persisted regardless of such an extraordinary and unsettling strike on the seat of American government is a sign of how premature it may be to conclude that Mr. Trump’s iron grip on his followers is at last loosening.

These were not isolated or trivial assertions from little-known people on the fringes of Mr. Trump’s movement. Rather, they came from some of his highest profile allies in conservative politics and media who helped enable his rise in the Republican Party and have aided him in his unrelenting assault on anyone who questions his actions.

Many Trump sympathizers were quick to try to shift the focus from the destructive scene in Washington and revive months-old stories about the fires and looting that accompanied some of the protests over police brutality and racial injustice following the killing of George Floyd in May.

On the floor of the House late Wednesday, Representative Matt Gaetz of Florida blamed anti-Trump saboteurs “masquerading as Trump supporters” for the violence and said, “I’m sure glad that at least for one day I didn’t hear my Democrat colleagues calling to defund the police.” That earned him a round of applause from his Republican colleagues.

After President Trump’s supporters stormed Capitol Hill, egged on by his rejection of the 2020 election results, a small but growing chorus of civic and business leaders and lawmakers released statements calling for his removal from power.

Some suggested that Vice President Mike Pence should invoke the 25th Amendment, which provides procedures that can be used to replace a sitting president who is no longer capable of fulfilling his duties.

“Vice President Pence, who was evacuated from the Capitol, should seriously consider working with the Cabinet to invoke the 25th Amendment to preserve democracy,” Jay Timmons, the president and chief executive of the National Association of Manufacturers, said in a statement on Wednesday afternoon.

Mr. Timmons, whose organization formerly had a tight working relationship with Mr. Trump, added that the “outgoing president incited violence in an attempt to retain power, and any elected leader defending him is violating their oath to the Constitution and rejecting democracy in favor of anarchy.”

He was not alone in making that suggestion. Representative Charlie Crist of Florida, who is now a Democrat but was formerly a Republican, posted on Twitter that “The 25th Amendment allows for the removal of a President. It’s time to remove the President.”

Representative Ted Lieu, Democrat of California, echoed that call on Twitter.

Seventeen Democratic members of the House Judiciary Committee signed a letter to Mr. Pence calling for the invocation of the 25th Amendment.

“Even in his video announcement this afternoon, President Trump revealed that he is not mentally sound and is still unable to process and accept the results of the 2020 election,” they wrote, referring to the video removed by Twitter.

By Wednesday night, other calls for removal were rolling in slowly but steadily, including from Gov. Phil Scott of Vermont, a Republican; Representative Mike Thompson, Democrat of California; Representative Earl Blumenauer, Democrat of Oregon; and other members of the House.

Concern centered on Mr. Trump’s rejection of a fair and peaceful transfer of power — he has repeatedly claimed, inaccurately, that the election was unfair or stolen — and on his failure to call off his supporters as they aggressively and illegally broke into the Capitol building on Wednesday.

Mr. Trump did eventually post a video suggesting they should leave, but in friendly terms.

“Go home, we love you,” he said.

A woman who was fatally shot inside the Capitol after it was overrun by a pro-Trump mob was struck by gunfire from a Capitol Police officer, a police official said Wednesday night.

Chief Robert J. Contee of the Metropolitan Police Department told reporters that the woman had been shot by a police officer on Wednesday afternoon as plainclothes police officers confronted the mob. She later died in a hospital, he said, and the shooting is being investigated.

At least 14 Capitol Police officers were injured during the demonstrations on Wednesday, Chief Contee said, including two who were hospitalized.

A video posted to Twitter earlier on Wednesday appeared to show a shooting in the Capitol.

The woman in the video appeared to climb onto a small ledge next to a doorway inside the building immediately before a single loud bang is heard. The woman, draped in a flag, fell to the ground at the top of a stairwell. A man with a helmet and a military-style rifle stood next to her after she fell, and shouts of “police” could be heard as a man in a suit approached the woman and crouched next to her.

“Where’s she hit?” people yelled as blood streamed around her mouth.

Chief Contee said that three other deaths were reported on Wednesday — one woman and two men — from the area around the Capitol. He said, without elaborating, that the three people appeared to have “suffered from separate medical emergencies which resulted in their deaths.”

Representative Jake LaTurner, Republican of Kansas, announced that he received a positive test result for the coronavirus on Wednesday night, after he spent the day participating in a failed effort to stop Congress from formally certifying President-elect Joseph R. Biden Jr.’s victory.

Mr. LaTurner, a first-term lawmaker who assumed office this month, took the test as part of travel guidelines from the District of Columbia that require visitors to be tested, according to a message from his Twitter account posted early Thursday. He was not experiencing any symptoms.

As a group of Trump supporters, many without masks, stormed the Capitol on Wednesday, members of Congress and their staffers crowded together to hide from the violence and chaos that unfolded. Senators were rushed in close quarters to safety through the Capitol tunnels.

Coronavirus cases in the United States on Wednesday continued to rise, with 255,730 daily cases and nearly 4,000 deaths reported. It was the country’s worst day of the pandemic so far, in both categories, though reporting delays over the holidays may have affected the totals.

Congress has come under fire for lacking consistent procedures to protect members and staff from the coronavirus. More than 100 members of Congress have either tested positive, quarantined or come into contact with someone who had the virus, according to GovTrack.

Mr. LaTurner does not plan to return to the House floor for votes until he is cleared to do so, a message from his Twitter account said.

Anyone traveling to Washington from a district with more than 10 coronavirus cases per 100,000 people must get a test within 72 hours of traveling, and visitors to the city must be tested within three to five days of arrival.

The U.S. Office of Government Ethics published financial disclosure forms on Thursday morning for Katherine Tai, the Biden administration’s expected nominee for the position of United States Trade Representative. Thai currently serves as chief trade counsel for the House Ways and Means Committee.

The forms show Ms. Tai’s assets are far more limited than many of the outgoing members of the Trump administration, like Wilbur Ross, the wealthy financier who serves as commerce secretary, and Ms. Tai’s predecessor as trade representative, Robert E. Lighthizer.

Ms. Tai has retirement accounts valued between $70,000 and $350,000, and other investment accounts valued between $425,000 and $1,050,000. She also owns residential real estate in San Francisco valued between $500,000 and $1 million, and has bank accounts with between $350,000 and $750,000 in cash.

But Ms. Tai also has liabilities, namely three mortgages of between $1 million and $2 million, according to the filing.

President-elect Joseph R. Biden Jr. announced his nomination of Judge Merrick Garland — whose Supreme Court nomination Republicans blocked in 2016 — to be attorney general, placing the task of repairing a beleaguered Justice Department in the hands of a centrist judge, according to a statement issued on Thursday by his transition team.

The announcement also included other key Justice Department nominations, including Lisa Monaco, a former homeland security adviser to President Barack Obama, as deputy attorney general; Vanita Gupta, the head of the department’s civil rights division under Mr. Obama, as the No. 3; and Kristen Clarke, a civil rights lawyer, as assistant attorney general for civil rights, which is expected to be a major focus of the department under Mr. Biden.

If confirmed, Judge Garland, who has sometimes disappointed liberals with his rulings, would inherit a department that grew more politicized under President Trump than at any point since Watergate. He would face vexing decisions about civil rights issues that roiled the country this year, whether to investigate Mr. Trump and his administration, and how to proceed with a tax investigation into Mr. Biden’s son.

“Our first-rate nominees to lead the Justice Department are eminently qualified, embody character and judgment that is beyond reproach, and have devoted their careers to serving the American people with honor and integrity,” Mr. Biden said in a statement. “They will restore the independence of the department so it serves the interests of the people not a presidency, rebuild public trust in the rule of law, and work tirelessly to ensure a more fair and equitable justice system.”

The nomination ended weeks of deliberation by Mr. Biden, who had struggled to make a decision as he considered who should fill a position that he became convinced will play an outsize role in his presidency. Mr. Biden’s nominations are expected to broadly win confirmation with Democrats taking control of the Senate by winning both seats up for grabs in Georgia’s runoff elections.

Mr. Biden, who spent many years as the top Democrat on the Senate Judiciary Committee and chaired it from 1987 to 1995, was said by aides to have long weighed what makes a successful attorney general and put pressure on himself to make the right pick. Outside groups also pressed him to appoint a person of color who would take a far more confrontational position with law enforcement. On Thursday, Mr. Biden praised his nominees, calling them “among the most accomplished legal minds in our country who also reflect the best of America’s full range of talents and background.”

“I am honored they accepted this call to serve at such a critical time in our nation’s history,” he said.

Judge Garland was initially considered a long shot for attorney general, in part because he is seen as politically moderate. In close cases involving criminal law, he has been significantly more likely to side with the police and prosecutors over people accused of crimes than other Democratic appointees. He also leaned toward deferring to the government in Guantánamo detainee cases that pit state security powers against individual rights.

Moreover, judges are only occasionally elevated directly to the position. The last was Judge Michael Mukasey of Federal District Court, whom George W. Bush appointed to run the Justice Department in 2007.

Megan Specia contributed reporting.

“We deplore the desecration of the United States Capitol building, the shedding of innocent blood, the loss of life, and the quagmire of dysfunction that threaten our democracy.”

Those words, spoken by Barry C. Black, the Senate chaplain, resounded through the government chamber in the early hours of Thursday, as he declaratively closed a joint session of Congress marred by violence with a prayer.

Delivered moments after President-elect Joseph R. Biden’s victory was certified by lawmakers who had worked through the night, and hours after a violent crowd of rioters urged on by President Trump had threatened to derail the process, Mr. Black’s prayer cut through the chamber with force.

He condemned the violence of the day, acknowledged divisions in the nation and called for healing and unity.

A Seventh-day Adventist minister and former Navy rear admiral known for his penchant for brightly colored bow ties, Mr. Black has been the Senate’s official clergyman for nearly two decades. His prayers in the chambers have long been laced with rebukes for the infighting of the lawmakers surrounding him, and his words have often served as a conscience check for those on both sides of the aisle.

That was never more true than on Thursday morning, as he warned lawmakers that their words could have great consequences.

“These tragedies have reminded us that words matter, and that the power of life and death is in the tongue,” he said. “We have been warned that eternal vigilance continues to be freedom’s price.”

His prayer also urged new unity in the face of the deep divisions among lawmakers and within the country, driving home a need to “see in each other a common humanity.” He sought to move both the lawmakers and the nation forward, saying that God had “strengthened our resolve to protect and defend the Constitution of the United States against all enemies domestic as well as foreign.”

“Use us to bring healing and unity to our hurting and divided nation and world,” he said. “Thank you for what you have blessed our lawmakers to accomplish in spite of threats to liberty.”

Call them rioters. Or armed insurrectionists. But Erica de Bruin, a political scientist who literally wrote the book on how to prevent coups, said she would not call it a coup.

“I don’t object to anyone wanting to use the term ‘coup’ at this point,” she said in an interview. “The word coup conveys seriousness, and I don’t want to police the language of politicians or activists or those trying to oppose Trump’s actions. But I don’t think we’re there yet.”

The crucial factor, she said, is that a coup attempt requires force or the threat of force from an organized armed group, usually, though not necessarily, a military. And while many in the violent mob of President Trump’s supporters that stormed the Capitol building on Wednesday were armed, they did not appear to be part of any organized paramilitary organization.

Naunihal Singh, a professor at the Naval War College whose research focuses on coups, said he did not think this was a coup because President Trump encouraged the insurrectionists in his capacity as head of their movement, but did not do so via the powers of the president. “We can deal with this sort of power grab far more easily than one which uses presidential authority, if we’re willing to treat him the same way we would treat any regular citizen doing the same,” he said. (Dr. Singh spoke in his personal capacity.)

The scenes at the Capitol bear an obvious resemblance to coups, which often involve an armed takeover of legislative buildings. But the resemblance, Dr. de Bruin said, is a superficial one.

“They’re emulating coup plotters,” she said. “But when coup plotters do that, it’s because they think that occupying that position makes them look like they are holding political power. No one thinks that this group is actually in control.”

Both experts, however, cautioned against concluding that this is not a serious threat to American democracy.

“Coups aren’t that common these days,” Dr. de Bruin said. “The way we tend to see democracies fail these days is through this subtle undermining and chipping away of democracy.”