The panel of House lawmakers investigating the January 6 riot at the U.S. Capitol last year is hearing testimony about how former President Donald Trump repeatedly pressured then-Vice President Mike Pence to thwart Congress from certifying that Democrat Joe Biden had won the presidency.

Pence was presiding over Congress as lawmakers were in the initial stages of the state-by-state count of Electoral College votes to verify Biden’s victory when about 2,000 Trump supporters stormed the Capitol to disrupt the proceeding.

Trump, in private and publicly at a rally near the White House just before Congress convened, implored Pence to reject the electoral count from states where Biden narrowly won and send the results back to the states where Republican-controlled legislatures could order another election or submit the names of Trump electors to replace those favoring Biden.

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But Pence, a Trump loyalist during their four years in the White House, refused, saying his role was limited by the Constitution to simply open the envelopes containing the Electoral College vote counts from each state.

As he opened the hearing, Democratic committee chairman Bennie Thompson said Pence “knew it was illegal” to overturn the election. “He knew it was wrong.”

A Pence legal adviser, retired conservative federal appellate court judge Michael Luttig, testified that he had advised Pence that he had no authority to upend the election result.

“If Vice President Pence had obeyed the orders of his president and declared Donald Trump the next president of the United States, notwithstanding that President Trump had lost the Electoral College vote as well as the popular vote … it would have plunged America into what would have been tantamount to a revolution and a constitutional crisis,” Luttig said.

Greg Jacob, who was counsel to former Vice President Mike Pence, left, and Michael Luttig, a retired federal judge, are sworn in to testify as the House select committee investigating the January 6, 2021, attack on the Capitol holds a hearing at the Capitol in Washington, June 16, 2022.

Greg Jacob, who was counsel to former Vice President Mike Pence, left, and Michael Luttig, a retired federal judge, are sworn in to testify as the House select committee investigating the January 6, 2021, attack on the Capitol holds a hearing at the Capitol in Washington, June 16, 2022.

But as Trump realized Pence would not upend the election results, Thompson said, “Donald Trump turned the mob on him, the mob that chanted, ‘Hang Mike Pence!'”

“I had no right to overturn the election,” Pence has since said, even though his role required him to also certify his own defeat to Democrat Kamala Harris, now the U.S. vice president.

With Pence announcing ahead of time that he would not accede to Trump’s demand, some of the rioters at the Capitol turned against him as they stormed past security barriers, scuffled with police and ransacked congressional offices. Some erected a gallows on the National Mall in sight of the Capitol.

Republican Representative Liz Cheney, the vocally anti-Trump vice chairperson of the House of Representatives panel investigating the insurrection, said last week that Trump, watching the mayhem unfold on television from the White House, told aides he agreed with the idea that Pence should be hanged.

“Maybe our supporters have the right idea,” he allegedly said. “Mike Pence deserves it.”

Cheney also said, “President Trump believed his supporters at the Capitol … and I quote, ‘were doing what they should be doing.'”

“This is what he told his staff as they pleaded with him to call off the mob, to instruct his supporters to leave,” Cheney said.

Briefing reporters ahead of Thursday’s hearing, committee staffers said the session will focus in part on how Trump’s pressure campaign put Pence’s life in danger.

“You’ll see new materials that documented that day, that documented the vice president where he was, what he was doing,” one committee aide said, speaking on condition of anonymity.

The committee showed a brief video clip of Marc Short, who served as Pence’s chief of staff, saying that Pence told Trump “many times” that he did not have the authority to overturn the Biden victory.

Short, who worried about Trump turning on Pence and reportedly alerted the Secret Service to a potential security threat to Pence’s life, will not be testifying live but clips of his videotaped deposition were aired during Thursday’s hearing.

In a video message previewing the public hearing, Cheney referenced a federal judge’s recent ruling that Trump’s arm-twisting of Pence likely violated two federal criminal statutes.

In response to the committee’s hearings, Trump issued a 12-page statement on Monday, calling the January 6 investigation an attempt by Democrats to prevent him from running again for president in 2024.

Democratic Congressman Pete Aguilar of California will lead Thursday’s presentation. He told NBC News that Trump knew violence had erupted at the Capitol when he “tweeted the vice president didn’t have the courage to do what was necessary” to overturn the election result.

Rep. Pete Aguilar, D-Calif., speaks as the House select committee investigating the January 6, 2021, attack on the Capitol holds a hearing at the Capitol in Washington, June 16, 2022.

Rep. Pete Aguilar, D-Calif., speaks as the House select committee investigating the January 6, 2021, attack on the Capitol holds a hearing at the Capitol in Washington, June 16, 2022.

Aguilar said Trump’s tweet was crucial “because that’s the point at which the president pointed, you know, to the mob and said it’s the vice president’s fault.”

News footage that was broadcast shortly after the riot showed the Secret Service moving quickly to evacuate Pence and his family from a ceremonial office to an undisclosed location. Aguilar said Thursday’s hearing will include never-before-seen photos of Pence in the undisclosed location.

Thursday’s hearing is the third in a series scheduled for this month that lays out how the insurrection occurred and Trump’s role in it by inviting his supporters to come to Washington and “fight like hell” to keep him in office.

More than 800 of them have been arrested on charges ranging from trespassing and vandalizing the Capitol to attacking police. Some ringleaders have been charged with seditious conspiracy.

On Monday, the House panel showed videotaped testimony from numerous White House and political aides saying they told Trump on election night to hold off on declaring victory, advice he ignored when he declared victory in the early hours of Nov. 4, 2020.

Former Attorney General William Barr and numerous aides have told the committee that in the weeks between the election and the insurrection, they told Trump his election fraud claims were baseless and that he had lost the election.

Barr said in taped testimony aired by the committee that many of Trump’s claims of voting irregularities were “completely bogus and silly.”

“Obviously, he lost the election,” Barr said. “There was zero base of evidence sufficient to overturn the election.”

VOA’s Masood Farivar contributed to this report.