Arizona House Speaker Rusty Bowers, a Republican 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, as well as Trump attorney Rudy Giuliani, according to The Arizona Republic, faced the first questions from the committee on Tuesday, establishing that he did support Trump's re-election bid.

Bowers and other state officials on the first panel did not deliver opening statements, but Rep. Adam Schiff, D-Calif., said the Republican House speaker of Arizona will talk about "conversations with the president, with Rudy Giuliani and John Eastman, what's the president's team asked of him and how his oath of office would not permit it."

A spokesperson said for the Arizona House of Representatives said that Bowers is appearing in response to a committee subpoena.

-ABC News' Ali Dukakis

Rep. Adam Schiff, D-Calif., described the pressure placed on state officials as a "dangerous precursor" to the violence the nation witnessed on Jan. 6, 2021.

"This pressure campaign brought angry phone calls and texts, armed protests, intimidation, and, all too often, threats of violence and death," Schiff said in his opening statement. "State legislators were singled out. So, too, were statewide elections officials. Even local elections workers, diligently doing their jobs, were accused of being criminals, and had their lives turned upside down."

Trump's supporters, Schiff said, saw his conduct toward local officials as "a call to action."

"The president's lie was -- and is -- a dangerous cancer on the body politic," Schiff said. "If you can convince Americans that they cannot trust their own elections, that anytime they lose, it is somehow illegitimate, then what is left but violence to determine who should govern?"

Vice Chair Liz Cheney, R-Wyo., in her opening statement, said the committee will provide evidence that Trump "had a direct and personal role" in a scheme to have key states send fake electors to Congress and for Vice President Mike Pence to overturn the results, "as did Rudy Giuliani, as did John Eastman."

"In other words, the same people who were attempting to pressure Vice President Mike Pence to reject electoral votes illegally, were also simultaneously working to reverse the outcome of the 2020 election at the state level," Cheney said.

Cheney said the public will learn about calls Trump made to officials of Georgia and other states, and asked, "As you listen to these tapes, keep in mind what Donald Trump already knew at the time he made those calls -- he had been told over and over again that his stolen election allegations were nonsense," she said, going on to play video testimony of Trump's attorney general Bill Barr.

Also raising threats of violence to election workers, Cheney said, "Donald Trump didn’t care about the threats of violence" and "made no effort to stop them; he went forward with his fake allegations anyway."

"Do not be distracted by politics," she added, as the former president and GOP allies continue to attack the committee's investigation. "This is serious. We cannot let America become a nation of conspiracy theories and thug violence."

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."

Rep. Adam Schiff, D-Calif., who led the hearing Tuesday focused on Trump's pressure campaign on state election officials, appeared to speak to Attorney General Merrick Garland and other prosecutors at the Department of Justice watching the committee unfold its findings, reminding the public that lawmakers will not be the ones to bring charges to Trump and allies.

"Whether his actions were criminal will ultimately be for others to decide. But what he did was without a doubt unconstitutional. It was unpatriotic, and it was fundamentally un-American," Schiff said.

The committee has appeared to make the case that Trump directly engaged in a conspiracy to defraud the government.