Joe Biden’s presidential campaign canceled a Friday event in Austin, Texas, after harassment from a pro-Trump contingent.

Texas has emerged as a battleground state in Tuesday’s presidential election, with polls showing the typically Republican stronghold now only marginally favoring President Donald Trump. The Biden campaign scheduled a Friday event in the state, in a bid to drum up last-minute support. 

But when the Biden campaign bus drove to Austin, it was greeted by a blockade of pro-Trump demonstrators, leading to what one Texas House representative described as an escalation “well beyond safe limits.”

The cancelation comes amid national anxiety about voter intimidation, a tactic the Trump campaign has implicitly endorsed.

Historian Dr. Eric Cervini was driving to help with the Biden campaign stop when he filmed a line of pickup trucks along the highway, many of them flying Trump flags. The drivers were “waiting to ambush the Biden/Harris campaign bus as it traveled from San Antonio to Austin,” Cervini tweeted.

“These Trump supporters, many of whom were armed, surrounded the bus on the interstate and attempted to drive it off the road,” he alleged. “They outnumbered police 50-1, and they ended up hitting a staffer’s car.”