Chairman Bennie Thompson convened the committee's fourth hearing this month shortly after 1 p.m. and previewed the pressure campaign he said Trump and his allies put on election officials in key states with the aim of overturning the 2020 election.

In his opening statement, Thompson said "pressuring public servants into betraying their oaths was a fundamental part of the playbook" and that, in 2020, only a handful of election officials in key states "stood between Donald Trump and the upending of American democracy."

"Everything we describe today -- the relentless, destructive pressure campaign on state and local officials -- was all based on a lie. Donald Trump knew it," Thompson said. "He did it anyway."

Explaining how the U.S. elects its president with the Electoral College system, Thompson also warned that "the lie hasn’t gone away" but is still "corrupting our democratic institutions," citing an example of a county commissioner in New Mexico who refused to certify primary results last week.

"People who believe that lie are now seeking positions of public trust," Thompson said. "If that happens, who will make sure our institutions don’t break under the pressure? We won’t have close calls. We’ll have catastrophe."

The House select committee has subpoenaed a British documentary filmmaker who had substantial access to Trump, his family and closest aides both before and after the Jan. 6 attack, according to a statement from the filmmaker obtained by ABC News.

A spokesperson for filmmaker Alex Holder, who began filming Trump for a project in September 2020, confirmed the subpoena, first reported by Politico.

Holder said he has "fully complied with all of the committee’s requests" and handed over footage which includes interviews with Trump, Donald Trump Jr., Ivanka Trump, Eric Trump, son-in-law Jared Kushner and Vice President Mike Pence, shot in the weeks around the Jan. 6 attack.

-ABC News' Ali Dukakis and Benjamin Siegel

Shaye Moss, a former election worker in Georgia, will testify Tuesday about the threats she said she and her family received in the aftermath of the 2020 race, according to a copy of her opening statement obtained by ABC News.

"Ever since December 2020, I have been under attack for just doing my job," the statement reads. "My mom too."

Moss will describe how they were the target of lies spread by Trump and Rudy Giuliani, including false accusations that they brought ballots into the State Farm Arena in a suitcase.

"People showed up at my grandmother's home trying to bust the door down and conduct a citizen's arrest of my mom and me," her statement reads. "The threats followed me to work. People would email the general email address for our office so everyone could see their threats and the hateful messages directed at me."

Georgia Secretary of State Brad Raffensperger, whom Trump asked to "find" just one vote over the margin by which he trailed President-elect Joe Biden in a now-infamous phone call on Jan. 2, 2021, will testify before the committee this afternoon, along with his blunt-spoken deputy, Gabe Sterling, after facing backlash from their own party for pushing back on Trump's claims of election fraud in Georgia.

Joining them will be Arizona House Speaker Rusty Bowers, who was pressured by Ginni Thomas, the wife of Supreme Court Justice Clarence Thomas, to decertify Biden's victory in the state, according to emails reviewed by ABC News. Bowers previously described to The Arizona Republic that Rudy Giuliani also called him after the election to pressure him to involve the state legislature to manipulate results in his state.

Former Fulton County election worker Shaye Moss, who was falsely accused by Giuliani and other Republicans of election fraud and smuggling "suitcases" of illegal ballots in Atlanta on election night, will testify on a second panel. She's said that she and her mother, another election worker, were subject to harassment and threats online even after Georgia election officials debunked fraud allegations.