Trump's former campaign manager Bill Stepien testified Monday before the House Jan. 6 committee that Trump was "growing increasingly unhappy" at the election results as the night wore on.
Son-in-law Jared Kushner tried to steer Trump away from attorney Rudy Giuliani and his far-flung theories of voter fraud that advisers believed were not true.
Former Justice Department official Richard Donoghue recalls breaking down one claim after another - from a truckload of ballots in Pennsylvania to a missing suitcase of ballots in Georgia -- and telling Trump "much of the info you're getting is false."
"He was becoming detached from reality," said former Attorney General William Barr, who resigned. "I didn't want to be a part of it."
The witnesses appeared before the House committee investigating the Jan. 6 Capitol attack as the panel focused on the "big lie," Trump's false claims of voter fraud that fueled the defeated Republican president's efforts to overturn the 2020 election and provoked a mob of his supporters to lay siege to the U.S. Capitol.
Most of those appearing did so in previously recorded testimony from closed door interviews over the course of the panel's yearlong investigation. The committee has interviewed some 1,000 witnesses and compiled 140,000 documents, and some members say they have uncovered enough evidence for the Justice Department to consider an unprecedented criminal indictment against the former president.
Chairman Rep. Bennie Thompson, D-Miss., opened Monday's hearing saying Trump "betrayed the trust of the American people" and "tried to remain in office when people had voted him out."
Stepien was to be a key witness Monday, but abruptly backed out of appearing live because his wife went into labor. The ex-campaign manager is still close to Trump, and had been subpoenaed for to appear.
MORE: The Jan. 6 Capitol attack, by the numbers
But the panel marched ahead after a morning scramble, showing previously recorded testimony from the ex-campaign manager and others close to the president as Trump latched on to repeated false claims about the election although those closest told him the theories of stolen ballots or rigged voting machines were not true.
Stepien described how the festive mood at the White House on election night turned as Fox News announced Trump had lost the state of Arizona to Joe Biden, and aides worked to counsel Trump on what to do next.
But he turned a deaf ear to them, choosing to listen instead to Giuliani, who was described as inebriated by several witnesses. Giuliani issued a general denial on Monday, rejecting "all falsehoods" he said were being said about him.
"My belief, my recommendation was to say that votes were still being counted, it's too early to tell, too early to call the race," Stepien said in the recorded testimony.
But Trump "thought I was wrong. He told me so."
Kushner testified that he told Trump the approach Giuliani was taking was not one he would take. But the president pushed back and said he had confidence in the attorney.
And Barr, who had previously testified in last week's blockbuster hearing that he told Trump the allegations being raised were bull--, revealed in gripping detail how was "as mad as I'd ever seen him" when the attorney general explained that the Justice Department would not take sides in the election.
SEE ALSO: Election lies spawn deadly attack on US Capitol
Monday's hearing also featured other live witnesses, including Chris Stirewalt, a former Fox News Channel political editor who declared on Election Night that Arizona was being won by Biden.
Thompson, D-Miss., and vice chair Rep. Liz Cheney, R-Wyo., were leading the hearing after last week's blockbuster session drew nearly 20 million Americans to see its prime-time findings.
For the past year, the committee has been investigating the most violent attack on the Capitol since the War of 1812 to ensure such an assault never happens again. Lawmakers hope to show that Trump's effort to overturn Joe Biden's election victory posed a grave threat to democracy.
A second group of witnesses testifying Monday was to be made up of election officials, investigators and experts who were likely to discuss Trump's responses to the election, including dozens of failed court challenges, and how his actions diverged from U.S. norms.
Among them those witnesses is the former U.S. attorney in Atlanta, BJay Pak, who abruptly resigned after Trump pressured Georgia state officials to overturn his presidential defeat. Trump wanted to fire Pak as disloyal, but Pak stepped down after Trump's call urging Georgia Secretary of State Brad Raffensperger to "find" enough votes to overturn Biden's win in the state became public.
The panel will also hear from former Philadelphia City Commissioner Al Schmidt, the only Republican on the election board and who faced down criticism as the state's election was called for Biden, and noted Washington attorney and elections lawyer Benjamin Ginsberg.
As he mulls another White House run, Trump insists the committee's investigation is a "witch hunt." Last week he said Jan. 6 "represented the greatest movement in the history of our country."
Nine people died in the riot and its aftermath, including a Trump supporter shot and killed by police. More than 800 people have been arrested in the siege, and members of two extremist groups have been indicted on rare sedition charges over their roles leading the charge into the Capitol.
In its prime-time hearing, the committee laid out how Trump was told over and over again by his trusted aides and officials at the highest levels of government that there was no election fraud on a scale that could have changed the outcome. But Trump pursued his false claims about the election and beckoned supporters to Washington on Jan. 6 to overturn Biden's victory as Congress was set to certify the Electoral College results.
Additional evidence is to be released in hearings this week focusing on Trump's decision to ignore the outcome of the election and the court cases that ruled against him.
Monday's hearing was also turning to the millions of fundraising dollars Trump's team brought in in the run-up to Jan. 6, according to a committee aide who insisted on anonymity to discuss the details.
The committee has said most of those interviewed in the investigation are coming forward voluntarily, although some have demanded subpoenas to appear in public. Stepien, who remains close to Trump, oversaw the "conversion" of Trump's presidential campaign to a "Stop the Steal" effort, according to a subpoena issued by the committee last fall. Stepien is now a top campaign adviser to the Trump-endorsed House candidate, Harriet Hageman, who is challenging Cheney in the Wyoming Republican primary election.
Trump spokesman Taylor Budowich suggested Sunday that the committee's decision to call Stepien was politically motivated.
Lawmakers indicated that perhaps their most important audience member over the course of the hearings may be Attorney General Merrick Garland, who must decide whether his department can and should prosecute Trump. They left no doubt as to their own view whether the evidence is sufficient to proceed.
"Once the evidence is accumulated by the Justice Department, it needs to make a decision about whether it can prove to a jury beyond a reasonable doubt the president's guilt or anyone else's," said Rep. Adam Schiff, D-Calif, a panel member.. "But they need to be investigated if there's credible evidence, which I think there is."
Rep. Jamie Raskin, D-Md., another member said on CNN he doesn't intend to "browbeat" Garland but noted the committee has already laid out in legal pleadings the criminal statutes members believe Trump violated.
"I think that he knows, his staff knows, the U.S. attorneys know, what's at stake here," Raskin said.
No president or ex-president has ever been indicted. Garland has not said whether he would be willing to prosecute.
Associated Press writers Farnoush Amiri and Jill Colvin in New York contributed to this report.