US government lawyers threatened to quit en masse as then-President Donald Trump hounded them almost daily to help overturn his 2020 election defeat, a congressional inquiry has heard.
Justice Department officials said they told Trump there was zero evidence for his claims of mass voter fraud.
The attorneys also testified that the president's plan to reverse his loss in key states was "a murder-suicide pact".
The panel is investigating last year's US Capitol riot as an attempted coup.
The House of Representatives select committee is seeking to build a case that Trump's efforts to stay in power in the lead-up to the violent raid by a horde of his supporters on Congress on 6 January 2021 amounted to illegal conduct.
Trump, a Republican, has described the inquiry as a "kangaroo court" designed to distract Americans from the "disaster" of Democratic-led governance and spiraling inflation ahead of November's mid-term elections.
With President Joe Biden
's popularity at an all-time low, Trump has been indicating he may run for president again in 2024.
Thursday's public hearing, the fifth so far, focused on a pressure campaign waged by Trump against the Department of Justice - the federal agency that enforces US law and is supposed to be independent from the White House.
Former acting Attorney General Jeffrey Rosen said Trump had reached out to him "virtually every day" before the attack on the Capitol, where lawmakers were assembled to certify Mr Biden's election win.
According to Rosen, Trump asked that the justice department issue a statement calling the election results into question, adding "leave the rest to me and the Republican congressmen".
Rosen said he refused. "We did not think they were appropriate based on the facts or the law," he told the committee.
Former acting Deputy Attorney General Richard Donoghue testified that he had knocked down Trump's "arsenal of [voter fraud] allegations" one by one in a 90-minute conversation in December 2020.
Committee member Adam Kinzinger, an Illinois Republican, noted that Trump administration officials had at one point investigated a bogus claim that Italian satellites switched votes from Trump to Biden.
"This is one of the best examples of the lengths to which President Trump would go to stay in power, scouring the internet to support his conspiracy theories," he said.
The session heard that at least five allies of Trump, who had supported his attempts to overturn the election, had asked for presidential pardons to protect them from any future prosecutions.
The session also heard of an explosive Oval Office showdown on the night of 3 January 2021 between Trump and three top justice department officials.
Trump outlined a plan during the meeting to replace Rosen with a loyalist named Jeffrey Clark, an environmental lawyer, who had no relevant experience to run the department, the committee heard.
On official headed paper, Clark had drafted a memo advising lawmakers in states that Trump narrowly lost on how to throw out their election results.
Pat Cipollone, then the White House counsel, had warned the letter would be "a murder-suicide pact", Donoghue said.
He testified that he, Rosen and another senior official, Steven Engel, warned the president there would be a mass exodus from the justice department if he installed Clark. Trump ultimately backed off the plan.
The committee said Clark had refused to answer its questions, invoking his right not to self-incriminate. Thursday's hearing was held shortly after it was reported that the FBI had raided Clark's home.
The BBC's Tara McKelvey, who was at the hearing, said the search of Clark's property raises the possibility of criminal charges over the alleged election plot, including against the former president himself.
Thursday's session also heard claims that six congressional Republicans had requested pre-emptive presidential pardons from Trump in case they were prosecuted after he left office for having backed his challenge to the election results.
Ex-White House aides named the lawmakers as Mo Brooks of Alabama, Matt Gaetz of Florida, Marjorie Taylor Greene of Georgia, Louie Gohmert of Texas, Scott Perry of Pennsylvania and Andy Biggs of Arizona. None of them received pardons.
Two more open hearings will take place next month before the committee prepares a report on the Capitol attacks.
The panel cannot bring charges against the former president, but is expected to refer its findings to the justice department.