A jury in Texas has cleared five pro-Trump activists but found one liable in a civil trial over a 2020 incident in which they surrounded a Joe Biden campaign bus on the highway.
Motorists aboard the bus had accused the six defendants of violating state laws and a federal law used to counter the Ku Klux Klan white supremacist group.
After a two-week trial, jurors ordered Eliazar Cisneros to pay $40,000 (£30,000) in damages for conspiring to intimidate the campaign and disrupt its activities.
But no liability was found on the part of his co-defendants Stephen and Randi Ceh, Joeylynn and Robert Mesaros or Dolores Park.
John Paredes, a co-counsel in the case, said the ruling is “especially significant in today’s climate of heightened political tension, and sends a strong signal to all Americans that anyone who engages in acts of political intimidation or violence in this upcoming election or any other election will be held accountable”.
But the five acquitted Texas residents, who have long presented the case as politically motivated, also hailed the result of the trial.
Co-defendant Mrs Mesaros told reporters outside court that she and her husband had felt “like zoo animals in the cage and mischaracterised and misrepresented, and we’re just ready to feel like normal people again”.
Nearly four years ago, the six defendants participated in a so-called “Trump train” – a caravan of the Republican nominee’s supporters in their vehicles – that swarmed Biden’s campaign bus as it travelled along the Interstate 35 highway.
Video footage of the incident appears to show roughly three dozen cars and trucks occupying every lane and swerving through traffic to box the bus in and slow it down to a crawl before driver Timothy Holloway makes an abrupt exit to lose them.
Mr Holloway and two passengers – former Biden campaign staffer David Gins and former Democratic state senator Wendy Davis – sued in 2021 over what they called an act of political violence.
Three Biden campaign events in the area were cancelled following the incident, which involved at least one collision. Trump praised those involved at the time with a social media post proclaiming: “I LOVE TEXAS!”
Lawyers on the case cited potential violations of Texas statutes on civil assault and civil conspiracy but also invoked the Ku Klux Klan Act of 1871 to “reaffirm that threats, intimidation, and force have absolutely no place in American politics”.
Prosecutors have wielded the long-disused federal statute in recent years amid a climate of heightened political polarisation. Monday’s ruling marks the first time it has found a defendant liable in the modern era.
While the Trump supporters acknowledged they had participated in the Trump train and many similar convoys, they denied pre-planning the event or intending to harm those on the bus.
Jurors were shown evidence, however, that Mr Cisneros, a US Navy veteran, helped come up with the idea to “escort” the bus.
The seven-member panel ruled that he must pay $30,000 in damages to the three plaintiffs and an additional $10,000 to the driver, Mr Holloway.
An attorney for Mr Cisneros said he plans to appeal.
Last year, two original co-defendants in the case privately settled the case and issued public apologies.
The city of San Marcos also paid out $175,000 to the plaintiffs last year over allegations that local law enforcement failed to provide help in spite of repeated pleas to 911 for a police escort.