An expert on political extremism testified on Tuesday in Denver District Court that Donald Trump stoked his followers into staging a violent attack on the U.S. Capitol on Jan. 6, 2021, during a hearing in a lawsuit seeking to declare the former president ineligible to appear on next year’s Colorado ballot.

A group of Republican and unaffiliated Colorado voters sued last month to prevent Colorado’s secretary of state from including Trump on the state’s 2024 primary ballot, alleging that he’s disqualified under a rarely invoked post-Civil War clause of the U.S. Constitution that bars certain officials who have “engaged in insurrection” from ever holding federal office.

Representing the petitioners, Eric Olson, a former Colorado solicitor general, argued on the second day of a planned weeklong hearing that attempts by Trump’s followers to keep Congress from certifying Democrat Joe Biden’s 2020 election amounted to an insurrection. The petitioner’s star witness asserted that evidence showed the mob had been under Trump’s command.

Trump’s lead attorney, Scott Gessler, a Republican former Colorado secretary of state, countered that Trump’s remarks in the run-up to and on Jan. 6 were typical political speech, including phrases and sentiments commonly expressed by Democrats.

Judge Sarah B. Wallace has said she intends to issue a decision by Thanksgiving to allow sufficient time for appeals before Colorado’s Jan. 5, 2024 deadline to certify the state’s March 5 primary ballot.

The Colorado lawsuit is one of several based on the 14th Amendment that have been filed around the country, including one scheduled to be heard on Thursday by the Minnesota Supreme Court. Trump’s campaign on Monday asked a court to throw out a similar lawsuit in Michigan, contending that the events of Jan. 6 were a “riot,” not an insurrection or rebellion.

In opening remarks on Monday, Gessler sought to portray the Colorado lawsuit as an attempt to circumvent the voters’ right to pick the next president.

“This court should not interfere with that fundamental value – that rule of democracy,” Gessler said. “It’s the people who get to decide, and this lawsuit seeks to cancel that principle.”

Chapman University sociology professor Peter Simi, who studies political violence and extremism, on Tuesday testified that Trump spent years developing a relationship with “far-right extremists,” including groups implicated in planning and carrying out violence on Jan. 6.

“That relationship that was established and built, I think, really underscores how much influence he has for far-right extremists, and how much they perceive him as essentially on their side or one of them,” said Simi, the author of a book about White supremacists and the role violence plays in their culture.

Simi said he was “very confident” that Trump directed the mob on Jan. 6.

“The goal really was focused on preventing the democratic transfer of power,” he said.

Evidence presented by Simi included Trump’s role promoting the “birtherism” conspiracy theory that challenged then-President Barack Obama’s legitimacy to serve as president.

“That was really the beginning, and then when he announced his presidency (campaign), that was a real clarion call for far-right extremists that this was someone you wanted to pay attention to,” Simi said, referring to Trump’s 2015 candidacy launch, when he said Mexico was sending drug dealers, criminals and rapists across the border.

Noting that Trump routinely promoted fears about stolen elections over the years, Simi contended that there was an overlap between extremists and the Trump campaign’s “Stop the Steal” movement after the 2020 presidential election.

Evidence presented by Olson included Trump’s remarks claiming the upcoming election would be fraudulent unless he won. In an Aug. 17, 2020, video played in court, Trump declared: “Because the only way we’re going to lose this election is if the election is rigged. Remember that.”

Simi said the pieces leading up to Jan. 6 began to fall into place when Trump was asked to denounce extremist groups during a debate with Biden but instead told the Proud Boys to “stand back and stand by.”

Then, Simi said, when Trump tweeted “Big protest in DC on Jan. 6. Be there will be wild!” on Dec. 16, 2020, extremist groups and many of the media figures they followed were “galvanized, mobilized, energized.”

It all culminated on Jan. 6 as Trump spoke to thousands of supporters gathered on the Ellipse, outside the White House.

“Fight like hell, and if you don’t fight like hell, we’re not going to have a country anymore,” Trump said.

Simi said Trump’s repeated calls to fight – he used variations of the word 20 times in the speech – were meant to be taken literally.

“There’s such a balance in favor of the fighting versus the one reference to marching peacefully to the Capitol,” he said. “For extremists, there would be a clear understanding that fighting was the real message, not being peaceful.”

Under cross-examination by Gessler, Simi acknowledged that many of the “communication strategies” he earlier said established a clear relationship between Trump and his “extremist” followers were common forms of speech in a variety of settings.

But Simi insisted that a rigorous academic analysis showed Trump’s use of the techniques – including a reliance on words with multiple meanings and delivering message “with a wink and a nod” – stood out.

“I can say he expressed a consistent pattern of messages over time that encouraged violence,” Simi said, referring to Trump. “He expressed messages over time that endorsed violence. And that’s very, I think, in clear terms, part of this pattern.”

At one point, Gessler quoted from the 1994 comedy movie “Dumb and Dumber,” starring Jim Carrey and Jeff Daniels, to make the point that people can hear what they want to hear, regardless of the speaker’s intention.

Gessler describes a famous scene where Carrey is talking to a woman and asks if she would be attracted to him if they were the only people left on earth. There would maybe be a 1-in-a-million chance, she responds.

“He says, ‘So, you’re telling me there’s a chance?'” Gessler said.

He asked Simi, “Would that describe a far-right extremist looking for something to latch onto and willing to disregard evidence to the contrary?”

Responding to Gessler’s questioning, Simi conceded that concern about a stolen election is a “common feature of modern politics” and that some of Trump’s opponents maintained that the 2016 election was stolen due to Russian interference.

Gessler also played a video montage of what he called “leading members of the Democrat Party and office-holders” urging their supporters to “fight,” with some echoing language Trump used in his Jan. 6 speech.

Simi responded that it was important to take into account past communication between speakers and their audience, and to have an understanding of both their relationship and the setting.

“Context is always important, whether you’re talking about violence or otherwise,” Simi said.

“What I’m getting at is, you basically focused on stuff that was relevant to far-right extremism, and you ignored the stuff that wasn’t relevant to far-right extremism,” Gessler said.

In brief testimony, a Syracuse University law professor and national security expert said Trump declined to use available options to repel the attack on the Capitol after it started.

“He should respond to his constitutional responsibilities to protect the security of the United States when there’s an assault on our democratic process,” William Banks said, referring to Trump.

Banks said he hasn’t seen any evidence that Trump moved to deploy any of the thousands of National Guard troops or other law enforcement officers under his command.

Acknowledging that he didn’t have direct knowledge about what conversations took place at the White House while the Capitol was under assault, Banks said of Trump: “I believe he was watching the television screen. And tweeting.”

The hearing is expected to cover constitutional questions on Wednesday, including testimony about whether the 14th Amendment clause cited by petitioners applies to the president.

Colorado Politics reporter Michael Karlik contributed to this report.