WATCH: Jan. 6 Committee hearings - Day 5

WASHINGTON (AP) -- The House Jan. 6 committee is using Thursday's hearing to show the pressure that Donald Trump put on the Justice Department to install a loyalist at the helm who would pursue the then-president's false claims of voter fraud and stop the certification of the 2020 election that Democrat Joe Biden won.

Before the hearing began, the PBS NewsHour's Nicole Ellis spoke with NewsHour White House Correspondent Laura Barrón-López to preview the hearing. Watch both events in the live player above.

It's the latest account of how close the United States came to having a constitutional crisis if the department leaders had not threatened to resign and the defeated incumbent was able to orchestrate a plan for the government to overturn election results in several pivotal states.

WATCH: Every public Jan. 6 committee hearing so far

Rep. Adam Kinzinger, R-Ill., led the hearing, saying it would show "how close we came to losing it all."

Some important takeaways from this month's fifth hearing of the committee that is investigating the causes of the insurrection at the Capitol on Jan. 6, 2021. The committee has been trying to make the case that Trump's efforts to reverse his loss resulted in the deadly siege after he sent supporters to the Capitol as Congress was certifying Biden's victory.

Trump's Justice Department in turmoil

Day after day, Trump pressured the department leaders to dig into false claims of election fraud after the November 2020 election.

Former Attorney General William Barr had described the swirl of false voter fraud theories coming from Trump's orbit as "wack-a-mole."

The department declined Trump's overtures because "we did not think they were appropriate," testified Jeffrey Rosen, who became acting attorney general after Barr stepped down.

The officials told Trump that states conduct their own elections, free from federal interference. But Trump only pressed harder, despite being told repeatedly there was no fraud.

At point in late December 2020, Trump asked Rosen what Rosen found to be a "peculiar" question: Do you know Jeff Clark?

Trump was eyeing Clark to take over at the department.

Who is Jeffrey Clark?

Clark led the civil division that handled environmental cases. He was introduced to Trump by a Republican congressman from Pennsylvania, a leader of the House's conservative Freedom Caucus.

Clark had been circulating a proposal that would have the legislatures from battleground states not to certify their election results. By holding back their electors for Biden, the disputed states could submit alternate electors loyal to Trump.

READ MORE: Federal agents search former Trump-era DOJ official Jeffrey Clark's home

Clark's ideas alarmed his colleagues, as did his sudden rise into Trump's orbit as a potential new acting attorney general.

"It may well had spiraled us into a constitutional crisis," testified Richard Donoghue, the former acting deputy attorney general.

At one heated meeting when Trump was floating Clark's rise with the others at the White House, Donoghue made the point that "Jeff Clark wasn't even competent to serve as attorney general."

When Clark shot back that he had worked on complicated civil and environmental matters, Donoghue retorted: "How about you go back to your office and we'll call you when there's an oil spill?"

Subpoenas served on 'fake electors'

The hearing was gaveled in as the Department of Justice escalated its own investigation, searching Clark's Virginia home this week as federal agents also served subpoenas across the country related to the scheme by Trump allies to create sets of fake electors with the intention of invalidating Biden's win.

The purpose of the searches was not immediately clear, but they came as the House committee has pressured the department to step up its investigation.

READ MORE: Capitol riot hearings to stretch into July, chairman says

Among those being investigated are Republican officials in key states, including those working on the fake electors in the run-up to Jan. 6, when Congress would be tallying the election results.

The chairman of the Georgia Republican Party, David Shafer, received a subpoena, and the Nevada GOP chair, Michael McDonald, turned over his phone to federal agents Wednesday when they approached him outside his car in Las Vegas and presented a warrant. That's according to people familiar with the matter who were not authorized to discuss the developments publicly and spoke on condition of anonymity.