WASHINGTON (AP) — Angry supporters of President Donald Trump stormed the U.S. Capitol Wednesday, marching through the building, shouting and waving Trump and American flags and forcing a halt to congressional deliberations over challenges to Joe Biden's Electoral College victory.

Senators were being evacuated. Some House lawmakers tweeted they were sheltering in place in their offices.

Demonstrators fought with Capitol Police and then forced their way into the building, not long after a huge rally near the White House during which Trump egged them on to march to Capitol Hill.

Lawmakers had convened for an extraordinary joint session to confirm the Electoral College results but protests erupted outside the Capitol and government office buildings were being evacuated.

Though fellow Republicans were behind the challenge to Biden’s 306-232 Electoral College victory, Senate Majority Leader Mitch McConnell sought to lower tensions and argued against it. He warned the country “cannot keep drifting apart into two separate tribes” with “separate facts.”

McConnell declared, “The voters, the courts and the states all have spoken."

But other Republicans, including House GOP leaders among Trump's allies were acting out the pleas of supporters at his huge Wednesday rally up Pennsylvania Avenue outside the White House to “fight for Trump.”

“We have to fix this,” said Rep. Steve Scalise of Louisiana, the GOP whip.

The last-gasp effort is all but certain to fail, defeated by bipartisan majorities in Congress prepared to accept the November results. Biden i s to be inaugurated Jan. 20.

Still, Trump vowed to he would “never concede” and urged the massive crowd to march to the Capitol where hundreds had already gathered under tight security.

“We will never give up,” Trump told his noontime rally.

Vice President Mike Pence was closely watched as he stepped onto the dais to preside over the joint session in the House chamber.

Pence has a largely ceremonial role, opening the sealed envelopes from the states after they are carried in mahogany boxes used for the occasion, and reading the results aloud. But he was under growing pressure from Trump to overturn the will of the voters and tip the results in the president’s favor, despite having no legal power to affect the outcome.

“Do it Mike, this is a time for extreme courage!” Trump tweeted Wednesday.

But Pence, in a statement shortly before presiding, defied Trump, saying he could not claim “unilateral authority" to reject the electoral votes that make Biden president.

Despite Trump’s repeated claims of voter fraud, election officials and his own former attorney general have said there were no problems on a scale that would change the outcome. All the states have certified their results as fair and accurate, by Republican and Democratic officials alike.

Arizona was the first of several states facing objections from the Republicans as Congress took an alphabetical reading of the election results.

Biden won Arizona by more than 10,000 votes, and eight lawsuits challenging the results have failed. The state’s Supreme Court on Wednesday upheld the dismissal of an election challenge.

The joint session of Congress, required by law, convened before a watchful, restless nation — months after the election, two weeks before the inauguration’s traditional peaceful transfer of power and against the backdrop of a surging COVID-19 pandemic.

Lawmakers were told by Capitol officials to arrive early, due to safety precautions with protesters in Washington. Visitors, who typically fill the galleries to watch landmark proceedings, were not allowed under COVID-19 restrictions.

The session also came as overnight results from Georgia's runoff elections put Democrats within reach of a Senate majority.

With the Senate results from Georgia streaming in and Democrats within reach of controlling the chamber, Trump amplified his pleas to stay in office as a veto check on the rival party. At the rally he said he had just talked to Pence and criticized Republicans who are not willing to fight for him as “weak.”

While other vice presidents, including Al Gore and Richard Nixon, also presided over their own defeats, Pence supports those Republican lawmakers mounting challenges to the 2020 outcome.

It's not the first time lawmakers have challenged results. Democrats did in 2017 and 2005. But the intensity of Trump's challenge is like nothing in modern times, and an outpouring of current and elected GOP officials warn the showdown is sowing distrust in government and eroding Americans' faith in democracy.

Sen. Mitt Romney, R-Utah, told reporters on Capitol Hill that Trump’s election challenge has “disgraced the office of the presidency."

“We'll proceed as the Constitution demands and tell our supporters the truth -- whether or not they want to hear it,” Romney said.

Still, more than a dozen Republican senators led by Josh Hawley of Missouri and Ted Cruz of Texas, along with as many as 100 House Republicans, were pressing ahead to raise objections to individual states' reports of Biden's wins.

Under the rules of the joint session, any objection to a state’s electoral tally needs to be submitted in writing by at least one member of the House and one of the Senate to be considered. Each objection will force two hours of deliberations in the House and Senate, ensuring a long day.

House Republican lawmakers are signing on to objections to the electoral votes in six states — Arizona, Georgia, Nevada, Michigan, Pennsylvania and Wisconsin.

Hawley has said he will object to the election results from Pennsylvania, almost ensuring a second two-hour debate despite resistance from the state's Republican senator, Pat Toomey, who said the tally of Biden's win is accurate.

Sen. Kelly Loeffler may challenge the results in her state of Georgia. She was defeated in Georgia's runoff to Democrat Raphael Warnock, but was welcomed by crowds of lawmakers in the chamber. She can remain a senator until he is sworn into office.

The other Senate runoff race between Republican David Perdue and Democrat Jon Ossoff remained too early to call Wednesday, though Ossoff declared he won. Perdue, who was seeking reelection, is ineligible to vote in the Senate because his term expired with the start of the new Congress Sunday.

The group led by Cruz is vowing to object unless Congress agrees to form a commission to investigate the election, but that seems unlikely.

Those with Cruz are Sens. Ron Johnson of Wisconsin, James Lankford of Oklahoma, Steve Daines of Montana, John Kennedy of Louisiana, Marsha Blackburn of Tennessee, Mike Braun of Indiana, Cynthia Lummis of Wyoming, Roger Marshall of Kansas, Bill Hagerty of Tennessee and Tommy Tuberville of Alabama.

Many of the Republicans challenging the results said they are trying to give voice to voters back home who don't trust the outcome of the election and want to see the lawmakers fighting for Trump.

Hawley defended his role saying his constituents have been “loud and clear” about their distrust of the election. “It is my responsibility as a senator to raise their concerns," he wrote to colleagues.

As criticism mounted, Cruz insisted his aim was “not to set aside the election” but to investigate the claims of voting problems. He has produced no new evidence.

Both Hawley and Cruz are potential 2024 presidential contenders, vying for Trump's base of supporters.

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Associated Press writers Andrew Taylor, Jill Colvin and Kevin Freking in Washington and Bill Barrow in Atlanta contributed to this report.