Donald Trump hounded the Justice Department to pursue his false election fraud claims, striving in vain to enlist top law enforcement officials in his desperate bid to stay in power and hosting a dramatic Oval Office showdown in which he weighed replacing the agency's leader with a more compliant lower-level official, according to testimony Thursday to the House panel investigating the Jan. 6, 2021, Capitol riot.

Three Trump-era Justice Department officials recounted a relentless pressure campaign from the president, including day after day of directives to chase unsupported allegations that the election won by Democrat Joe Biden had been stolen. The officials described the constant contact as a stark breach of protocol for a department that cherishes its independence from the White House but said they swatted away each demand because there was zero evidence of widespread voter fraud.

“For the department to insert itself into the political process this way, I think would have had grave consequences for the country that very well may have spiraled us into a constitutional crisis,” said Richard Donoghue, the acting No. 2 official in the final days of the Trump administration.

The president, he said, had this "arsenal of allegations. I went through them piece by piece to say, no, they were not true.”

Another witness, Jeffrey Rosen, who was acting attorney general, said he was called by Trump or met with him basically every day from the time he ascended to the post in late December 2020 through early January 2021, with the common theme being “dissatisfaction about what the Justice Department had done to investigate election fraud.”

It all added up to a “brazen attempt” to use the Justice Department for his own political gain, said Rep. Bennie Thompson, a Mississippi Democrat and co-chairman of the Jan. 6 committee.

“Donald Trump didn’t just want the Justice Department to investigate,” Thompson said. “He wanted the Justice Department to help legitimize his lies, to basically call the election corrupt” and to appoint a special counsel. The Justice Department resisted each demand.

As in past hearings, the committee focused on lawmakers who'd aligned themselves with Trump's efforts. On Thursday, the panel played recorded interviews of Trump aides saying that multiple Republican members of Congress requested pardons in the days after the violent riot at the Capitol.

Testimony also centered on a tense Oval Office showdown on Jan. 3, 2021, in which Trump contemplated replacing Rosen with a lower-level official, Jeffrey Clark, who wanted to champion Trump's bogus election fraud claims. Donoghue and another senior Justice Department official, Steven Engel, warned Trump that there would be mass resignations at the department if Trump followed through with his plan. Only then did Trump relent.

Clark's name was referenced early in the hearing, with Rep. Adam Kinzinger, an Illinois Republican, deriding him as a lawyer whose sole qualification was his fealty to Trump. A lawyer for Clark did not return an email ahead of the hearing.

“Who is Jeff Clark?” Kinzinger asked rhetorically. "He would do whatever the president wanted him to do, including overthrowing a free and fair democratic election.”

Barely an hour before the hearing began, it was revealed that federal agents this week searched Clark’s Virginia home, according to a person familiar with the matter who was not authorized to discuss it by name and spoke on condition of anonymity. A spokesman for the U.S. attorney confirmed the existence of law enforcement activity in Virginia, where Clark lives, but would not say what it was connected to.

The panel's hearing was the fifth this month by the House committee investigating the run-up to the insurrection at the Capitol, when Trump loyalists stormed the building as lawmakers were certifying the results of the election won by Biden. Witnesses have included police officers attacked at the Capitol as well as lawyers, a television executive and local election officials who all resisted demands to alter results in Trump's favor.

The committee last week presented videotaped depositions of former Attorney General William Barr, who castigated Trump's fraud claims and resigned after failing to convince the president.

Thursday's hearing focused on what happened next as Rosen, Barr's top deputy, took over the department and found himself immediately besieged by Trump's demands for action.

In one phone conversation, according to handwritten notes taken by Donoghue and highlighted at Thursday's hearing, Trump directed to Rosen to “Just say the election was corrupt and leave the rest to me and the R. Congressmen."

Around that time, Trump was introduced by a Republican congressman, Rep. Scott Perry of Pennsylvania, to Clark, who'd joined the department in 2018 as its chief environmental lawyer and was later appointed to run its civil division. Clark has been subpoenaed by the committee but was not among the witnesses Thursday. Lawmakers on Thursday played a videotaped deposition showing him repeatedly invoking his constitutional right against self-incrimination.

Clark, according to statements from other Justice Department officials, met with Trump despite being ordered not to by bosses at the department and presented himself as eager to aid the president's efforts to challenge the election results. A report released last year by the Senate Judiciary Committee that painted Clark as a relentless advocate for Trump included a draft letter pushing Georgia officials to convene a special legislative session to reconsider the election results.

Clark wanted the letter sent, but superiors at the Justice Department refused.

The situation came to a head on Jan. 3, 2021, a Sunday, when Clark informed Rosen in a private meeting at the Justice Department that Trump wanted to replace him with Clark as acting attorney general. Rosen, resisting the idea of being fired by a subordinate, said Thursday that he contacted senior Justice Department officials to rally them together and also requested a White House meeting.

That night, Rosen, Donoghue and Engel, along with Clark, gathered with Trump and top White House lawyers for a contentious, hours-long Oval Office meeting about whether the president should follow through with his plans for a radical leadership change at the department.

According to testimony given by Rosen, Trump opened the meeting by saying, “One thing we know is you, Rosen, aren’t going to do anything to overturn the election.”

Donoghue and Engel made clear to Trump that they and large numbers of other Justice Department officials would resign if Trump fired Rosen. White House lawyers said the same. Pat Cipollone, then the White House counsel, said the letter that Clark wanted to send was a “murder-suicide pact.”

“Steve Engel at one point said, ‘Jeff Clark will be leading a graveyard. And what are you going to get done with a graveyard,’ that there would be such an exodus of the leadership,” Donoghue told the Senate Judiciary Committee. “So it was very strongly worded to the president that that would happen.”

Donoghue also sought to dissuade Trump from believing that Clark had the legal background to do as the president wished since he was not a criminal prosecutor at the department.

“And he kind of retorted by saying, ‘Well, I’ve done a lot of very complicated appeals and civil litigation, environmental litigation, and things like that,’” Donoghue said. “And I said, ‘That’s right. You’re an environmental lawyer. How about you go back to your office, and we’ll call you when there’s an oil spill.’”