WASHINGTON (AP) — The 1/6 committee is set to plunge into Donald Trump’s last-ditch effort to salvage the 2020 election by pressuring Vice President Mike Pence to reject the electoral count — a highly unusual and potentially illegal strategy that was set in motion in the run-up to the U.S. Capitol riot.

With two live witnesses Thursday, the House panel intends to show how Trump’s false claims of a fraudulent election left him grasping for alternatives as courts turned back dozens of lawsuits challenging the vote.

Trump latched onto conservative law professor John Eastman’s obscure plan and launched a public and private pressure campaign on Pence days before the vice president was to preside over the Jan. 6 joint session of Congress to certify Joe Biden’s election victory. A federal judge has said it is “more likely than not” Trump committed crimes over the scheme.

“The illegality of the plan was obvious,” the Jan. 6 panel said in a court filing against Eastman.

The committee will hear from Greg Jacob, the vice president’s counsel who fended off Eastman’s ideas for Pence to carry out the plan; and retired federal judge Michael Luttig, who called the plan from Eastman, his former law clerk, “incorrect at every turn.”

Thursday’s session is also expected to divulge new evidence about the danger Pence faced that day as the mob stormed the Capitol shouting “hang Mike Pence!” with a gallows on the Capitol grounds as the vice president fled with senators into hiding. Nine people died in the riot and its aftermath.

The session is expected to show how Trump’s pressure on Pence “directly contributed” to the attack on the Capitol and how the Eastman strategy posed a “grave, grave threat” to democracy, according to a committee aide who insisted on anonymity to discuss the upcoming hearing.

Ahead of the hearing, Pence’s former chief of staff, Marc Short, said his boss was determined to stay at the Capitol that night and finish the job, despite the threats.

“He knew his job was to stay at his post,” Short said on CNN on Wednesday.

Short said Pence didn’t want the world seeing the vice president leaving the Capitol when “a hallmark of democracy” was under siege.

“He thought it was important that he stay there and make sure the work of the American people was completed that night,” said Short, who testified under subpoena to the committee for eight hours, but has not yet appeared as a live witness.

The panel is reconvening for a third hearing this month after a blockbuster prime-time start last week, followed by logistical setbacks in recent days. Monday’s key witness, former Trump campaign manager Bill Stepien, abruptly declined to appear in person because his wife was in labor with their child. Wednesday’s scheduled hearing with witnesses from the Justice Department who tried to convince Trump that his claims of voter fraud were just not true was postponed.

Nevertheless, the panel’s yearlong investigation is portraying a publicly gripping account of Trump’s final weeks in office as the defeated president clung to “the big lie” of a rigged election even as those around him — his family, his top aides, officials at the highest levels of government — were telling him he simply lost the election.

Former Attorney General William Barr, who resigned at the end of 2020 rather than be part of Trump’s plans, testified earlier that the president was becoming “detached from reality” if he believed the lies. He said he told the president his claims of voter fraud were “bull-—.”

With 1,000 interviews and reams of 140,000 documents, the committee is connecting the dots, showing how Trump’s false claims of election fraud became a battle cry as he summoned thousands of Americans to Washington for a Jan. 6 rally and then sent them to Capitol Hill to “fight like hell” for his presidency.

More than 800 people have been arrested in the Capitol siege, and the panel is considering whether to send a referral for criminal charges against Trump to the Justice Department. No president or former president has ever been indicted by the Justice Department, and Attorney General Merrick Garland has said he and his team are following the proceedings in Congress.

For now, the panel is pressing ahead with its hearings, with more scheduled for next week.

Thursday’s will unpack the Eastman plan to have the states send alternative slates of electors from the five or seven states Trump was disputing, including Arizona, Georgia, Michigan, Pennsylvania and Wisconsin. With competing slates for Trump or Biden, Pence would be forced to reject them, returning them to the states to sort it out, under the plan.

Pence refused the plan, believing the founding fathers would not have left it to one person, the vice president, to decide the outcome, Jacob told the panel in previous testimony. Jacob said the idea was utterly against some 130 years of precedent in American history, “entirely made up.”

The committee in hearings ahead will be delving into the roles of extremist groups and others who heeded Trump’s call to Washington. Leaders and others from the Oath Keepers and Proud Boys face rare sedition charges over their roles in the Capitol attack.

Several members of Congress are also under scrutiny, including Rep. Barry Loudermilk, R-Ga., whom the committee has asked for an interview to discuss a Capitol tour he gave that included basement tunnels to a group of people the day before the attack.

The panel is also probing several candidates for elected office, including the Republican nominee for governor in Pennsylvania, who were among the rioters.

The panel, which is expected to deliver a final report on its findings later this year, intends for its work to be a record for history of the most violent attack on the Capitol since the War of 1812. Unlike other national traumas that have pulled the country together, the Jan. 6 Capitol attack appears to have left many Americans divided. Congress splintered over forming the committee, which most Republicans opposed.

The panel’s two Republicans, Rep. Liz Cheney of Wyoming and Rep. Adam Kinzinger of Illinois, have been shunned by the GOP for their work with Democrats leading the investigation into Trump and his role in the Capitol attack.