AUSTIN, Texas (AP) — A federal trial is set to begin Monday over claims that supporters of former President Donald Trump threatened and harassed a Biden-Harris campaign bus in Texas four years ago, disrupting the campaign on the last day of early voting.

The civil trial over the so-called "Trump Train" comes as Trump and Vice President Kamala Harris race into the final two months of their head-to-head fight for the White House in November.

Democrats on the bus said they feared for their lives as Trump supporters in dozens of trucks and cars nearly caused collisions, harassing their convoy for more than 90 minutes, hitting a Biden-Harris campaign staffer's car and forcing the bus driver to repeatedly swerve for safety.

"For at least 90 minutes, defendants terrorized and menaced the driver and passengers," the lawsuit alleges. "They played a madcap game of highway 'chicken' coming within three to four inches of the bus. They tried to run the bus off the road."

The highway confrontation prompted an FBI investigation, which led then-President Trump to declare that in his opinion, "these patriots did nothing wrong."

Among those suing is former Texas state senator and Democratic nominee for governor Wendy Davis, who was on the bus that day. Davis rose to prominence in 2013 with her 13-hour filibuster of an anti-abortion bill in the state Capitol. The other three plaintiffs are a campaign volunteer, staffer and the bus driver.

The lawsuit names six defendants, accusing them of violating the "Ku Klux Klan Act," an 1871 federal law to stop political violence and intimidation tactics.

The same law was used in part to indict Trump on federal election interference charges over attempts to overturn the results of the 2020 election in the run-up to the Jan. 6 U.S. Capitol insurrection. Enacted by Congress during the Reconstruction Era, the law was created to protect Black men's right to vote by prohibiting political violence.

Videos of the confrontation on Oct. 30, 2020, that were shared on social media, including some recorded by the Trump supporters, show a group of cars and pickup trucks — many adorned with large Trump flags — riding alongside the campaign bus as it traveled from San Antonio to Austin. The Trump supporters at times boxed in the bus, slowed it down, kept it from exiting the highway and repeatedly forced the bus driver to make evasive maneuvers to avoid a collision, the lawsuit says.

On the two previous days, Biden-Harris supporters were subjected to death threats, with some Trump supporters displaying weapons, according to the lawsuit. These threats in combination with the highway confrontation led Democrats to cancel an event later in the day.

The lawsuit, which seeks unspecified monetary damages, alleges the defendants were members of local groups near San Antonio that coordinated the confrontation.

Francisco Canseco, an attorney for three of the defendants, said his clients acted lawfully and did not infringe on the free speech rights of those on the bus.

"It's more of a constitutional issue," Canseco said. "It's more of who has the greater right to speak behind their candidate."

Judge Robert Pitman, an appointee of former President Barack Obama, is set to preside over Monday's trial. He denied the defendants' pretrial motion for a summary judgment in their favor, ruling last month that the KKK Act prohibits the physical intimidation of people traveling to political rallies, even when racial bias isn't a factor.

While one of the defendants, Eliazar Cisneros, argued his group had a First Amendment right to demonstrate support for their candidate, the judge wrote that "assaulting, intimidating, or imminently threatening others with force is not protected expression."

"Just as the First Amendment does not protect a driver waving a political flag from running a red light, it does not protect Defendants from allegedly threatening Plaintiffs with reckless driving," Pitman wrote.

A prior lawsuit filed over the "Trump Train" alleged the San Marcos Police Department violated the Ku Klux Klan Act by failing to send a police escort after multiple 911 calls were made and a bus rider said his life was threatened. It accused officers of privately laughing and joking about the emergency calls. San Marcos settled the lawsuit in 2023 for $175,000 and a requirement that law enforcement get training on responding to political violence.

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Lathan is a corps member for The Associated Press/Report for America Statehouse News Initiative. Report for America is a nonprofit national service program that places journalists in local newsrooms to report on undercovered issues.