Former deputy acting attorney general Richard Donoghue illustrated how serious discussions were of mass resignations at the Justice Department as Trump threatened to replace his attorney general with a lower-level official who supported his plan to overturn the election, describing his fears of the potential impact that it could have in the final days of Trump administration.

Donoghue said he pleaded separately with the head of DOJ's national security division, John Demers, to not be among those who would resign.

"I prefaced the call by saying, 'John, we need you to stay in place. National security is too important and we need to minimize the disruption,'" Donoghue said in the hearing.

Donoghue said while Demers showed a willingness to resign, he agreed with Donoghue's assessment, as they imagined what would happen to the nation's top law enforcement agency should all the top officials resign.

"As Steve Engel noted, the goal was to make clear to Trump he would leave Clark leading a "graveyard," a comment that "clearly had an impact on the president," Donoghue said.

While discussing whether to fire a top official in the Department of Justice in a 2.5 hour meeting at the Oval Office on Jan. 3, 2021, Trump turned to officials in the room and asked them a question, former deputy attorney general Richard Donoghue testified Thursday.

"What do I have to lose?" Trump asked, according to Donoghue.

"It was actually a good opening," Donoghue said. "And I began to explain to him what he had to lose, and what the county had to lose and what department had to lose, and this was not in anyone's best interest."

Donoghue said no one in the room supported Jeffrey Clark taking over as the department's top official, describing him to the president as unqualified. Clark at the time was a Trump-appointed Justice Department official overseeing the department's Civil Division and environmental enforcement matters.

According to call logs displayed by the committee, the White House had already begun referring to Jeffrey Clark as "acting attorney general" on Jan. 3, 2021 -- despite Jeff Rosen, who wouldn't fall in line with election fraud conspiracies, actually serving as acting attorney general.

Trump also met with the aforementioned officials in the Oval Office on Jan. 3, and said, according to Rosen, "'Well the one thing we know is you're not gonna do anything. You don't even agree that the concerns that are being presented are valid. And here is someone who has a different view, so, why shouldn't I do that?'"

Former deputy acting attorney general Richard Donoghue recalled asking attorney generals across the country what they would do if Clark was put in charge.

"All essentially said they would leave," he told the panel. "They would resign en masse if the president made that change in the department leadership."

A hard-right conservative member of the House and leader of the House Freedom Caucus, Rep. Scott Perry, R-Penn., has been one of Trump's most loyal supporters in Congress.

As the Jan. 6 committee laid out Thursday, that support continued after the 2020 election, when he was among the Republicans who met with Trump at the White House on Dec. 21, 2020, on how to continue challenging Joe Biden's victory and push claims of voter fraud.

The next day, Perry introduced Jeffery Clark to Trump in a White House meeting. Clark did not work on election issues at the Justice Department, and he met with the president without the knowledge of his superiors in violation of DOJ rules.

"So, for criminal matters, the policy for a long time has been the only the attorney general in the deputy attorney general from the DOJ side can have ... conversations with the White House," Jeffrey Rosen, the then-acting attorney general, told the committee.

Why was Clark recommended? Here's how Rudy Giuliani explained it, in his recorded interview with the committee: “I do recall saying to people that somebody should be put in charge of the Justice Department who isn't frightened of what is going to be done to their reputation.”

Richard Donoghue, the acting deputy attorney general at the time, said Perry wanted Clark to "take over" the Justice Department, and pushed Mark Meadows, the White House chief of staff and his former House colleague, to make it happen.

-ABC News' Benjamin Siegel

Former acting deputy attorney general Richard Donoghue said he tried to convey to Jeffrey Clark that a draft letter he circulated seeking to ask Georgia's governor and other top state officials to convene the state legislature into a special session to investigate claims of voter fraud -- which didn't exist -- could launch the country into a "constitutional crisis."

"I had to read both emails and the attached letter twice to make sure I really understood what he was proposing -- because it was so extreme to me, I had a hard time getting my head around it initially," he recalled, adding he and former acting attorney general Jeffrey Rosen had "visceral reactions to it."

"I thought it was very important to get a prompt response rejecting this out of hand. In my response, I explained a number of reasons that this is not the department's rule to suggest or dictate [to] state legislatures," he said.

"More importantly, this was not based on fact. This was actually contrary to the facts as developed by department investigations over the last several weeks and months," he added. "For the department to insert itself into the political process this way, I think, would have had great consequences for the country. It may very well have spiraled into a constitutional crisis -- and I want to make sure that he understood the gravity of the situation because he did not seem to really appreciate it."