Pence, too, played a role in ushering in Biden's presidency. The vice president was constitutionally required to preside over the session and faced intense pressure from Trump to assert non-existent authority to unilaterally overturn the election results. And although he had already told Trump he would do no such thing, he returned to the Capitol after the riots with an even more forceful message.

"To those who wreaked havoc in our Capitol today, you did not win," Pence said.

Congressional leaders delivered similarly defiant remarks upon their return to the Capitol. "We must and we will show to the country — and indeed to the world — that we will not be diverted from our duty," Pelosi said. "To those who engaged in the gleeful desecration of this, our temple of democracy, justice will be done."

Senate Minority Leader Chuck Schumer, who earlier in the day was in a celebratory mood over his party's surge to victory in two Georgia Senate runoffs — likely catapulting him to majority leader later this month — pinned the violence on Trump's incitement and said Jan. 6, 2021 would go down alongside the attack on Pearl Harbor as a day that will "live in infamy." Senate Majority Leader Mitch McConnell labeled the riots a "failed insurrection."

"We're going to go back and do our business," Sen. Joe Manchin (D-W.Va.) told reporters. "Whatever it takes. These thugs are not running us off."

At around 10:30 p.m., the Senate rejected a challenge to Arizona's Electoral College votes, 6-93. The riot in the Capitol earlier in the day caused at least eight Senate Republicans to withdraw their objections to Biden's Electoral College win, but Sens. Josh Hawley (R-Mo.), Ted Cruz (R-Texas), Cindy Hyde-Smith (R-Miss.), Roger Marshall (R-Kan.), Tommy Tuberville (R-Ala.) and John Kennedy (R-La.) voted in favor. The House followed suit, shooting down the challenge overwhelmingly, even though 121 Republicans — more than half of the GOP conference — supported it.

Shortly before 1 a.m., the Senate rapidly dispensed with a challenge to Pennsylvania's votes as well, rejecting the Hawley-led effort 7-92 without any debate. The House rejected the challenge 138-282 shortly after 3 a.m.

But the tumultuous day and long night appeared to wear on lawmakers.

"A woman died out there tonight, and you're making these objections," said Rep. Conor Lamb (D-Pa.), gesturing at Republicans and accusing them of "lies" that he said were the same ones that inspired Wednesday's riot. His comments led to a shouting match in the chamber as Republicans asked Pelosi to strike his words.

The direct threat to lawmakers, which was followed by shocking footage of pro-Trump rioters forcing their way into rooms believed to be the most secure in the country, seemed to sharpen bipartisan fury aimed at Trump. The president remained disengaged while the violence escalated, twice tweeting muted calls for peace and recording a video in which he told the rioters "we love you" while encouraging them to go home. He later tweeted of the violence, "These things happen," reiterating his false claims of a stolen election.

While Trump withdrew during the chaos, lawmakers were barricaded in the House chamber while rioters flooded the Capitol, breaking windows, accessing secure areas and hammering on the doors of the House chamber, where Capitol Police drew guns in preparation for a breach. As they sheltered from the mob, some lawmakers tweeted condemnations of Trump, calls for his impeachment and bipartisan rebukes of the president for doing little to try to quell the unrest, even after it consumed the Capitol. Meanwhile, supporters barged into Pelosi's office and took photos sitting in her chair.

"What happened at the U.S. Capitol today was an insurrection, incited by the president of the United States," Sen. Mitt Romney (R-Utah) said.

The chaos exploded shortly after Pence rejected Trump’s last-ditch campaign to reverse the 2020 election results, delivering the fatal blow to the president's attempt to subvert Biden's win. "It is my considered judgment that my oath to support and defend the Constitution constrains me from claiming unilateral authority to determine which electoral votes should be counted and which should not," Pence wrote in a letter to lawmakers just before arriving at the Capitol.

Before the delay, Pence had hinted that he’d operate in the traditional mold of vice presidents at these crucial transition-of-power sessions, despite Trump's increasingly pointed entreaties, which continued Wednesday morning.

In fact, no challenges to electors have ever been upheld. The last time objectors forced a debate came in 2005, when Democrats cited irregularities in Ohio's election results. The challenge was easily swept aside in both chambers. House Democrats also objected to the results in 2001 and 2017 but no senators joined them.

Republicans also entered Wednesday in a deflated state after losing one Senate runoff race in Georgia. The other Georgia Senate race was called for the Democratic candidate later Wednesday, an outcome that will relegate the GOP to minority status in the chamber and dash Republicans' hopes of operating as a counterweight to the Biden presidency. That development had already led some of Trump's Republican detractors to question the wisdom of proceeding with a process aimed at delegitimizing the election results.

Lawmakers in both parties spent much of this week strategizing over the floor antics, including Pelosi, who had worked with key state delegation leaders on details such as the order of speeches on the floor. Congressional leaders had also discussed how to keep another threat — the coronavirus — at bay while hundreds of lawmakers were on the floor. On Tuesday afternoon, the Capitol physician issued a memo urging lawmakers to maintain distance in the chamber — a difficult task with the entire Congress forced to spend at least some time in the House chamber at the same time.