Updated at 8:40 p.m. with Trump responding to FBI investigation.

WASHINGTON — Stumping on Sunday as passions flared before the election, President Donald Trump commended supporters who had swarmed a Biden campaign bus in Texas two days earlier, leaving passengers shaken.

One pickup that tailgated the bus on the highway between San Antonio and Austin swerved into a car full of Biden campaign workers, leaving deep dents in the passenger side.

“Did you see the way our people were protecting his bus?” Trump boasted at a frigid rally in Washington, Mich., hours after he’d tweeted video of the caravan with the message: “I LOVE TEXAS.” “They had hundreds of cars. Trump. Trump. Trump, and the American flag.”

“These patriots did nothing wrong," he tweeted Sunday night in response to news the FBI was investigating.

Polls show that most Americans expect violence on Election Night or in the days that follow. Tensions are high. And to the dismay of some, the president is not lowering the temperature.

“It sort of boggles my mind that he didn’t recognize this as an act of electoral intimidation and harassment,” said Idean Salehyan, a University of North Texas political scientist and executive director of the Peace Science Society, a group of scholars who study political conflict and conflict resolution. “He’s not directly egging it on but … what was done was clearly reprehensible, and rather than condemning it, his reaction is to praise his supporters.”

Former vice president Joe Biden chastised the president for siding with the drivers who swarmed his campaign bus south of Austin.

“We’ve never had anything like this — at least we’ve never had a president who thinks it’s a good thing,” he said Sunday while stumping in Philadelphia.

Liberal detractors compared the “Trump Train” caravan to brown shirts, the paramilitary arm of the Nazi Party whose thuggery paved the way for Hitler’s rise to power.

The comparison is vastly overblown. One key difference: The violence seen in the run-up to Election Day, including Friday’s incident south of Austin on Interstate 35, has not been centrally coordinated, or brutal.

Still, it represents a serious departure in a country with a tradition of settling its differences at the ballot box.

Texas elections have not been marred with such confrontations in recent memory.

It could have been a prank that got out of hand.

It could reflect frustration, anger and fear that the political balance is shifting. Polls show Texas at a tipping point, potentially slipping from control of conservative Republicans for the first time in a generation.

Texas GOP chairman Allen West declined to discuss the incident on Sunday, referring to a statement from Saturday asserting that a query from the Texas Tribune about it was an “attempt to portray conservatives as violent radicals, even though it is leftists from Antifa and BLM who have been assaulting, robbing, and looting fellow citizens and their property.”

No prominent Texas Republicans have condemned the drivers involved in Friday’s incident. Trump spokespeople in Texas and at campaign headquarters did not respond to queries.

Sen. Kamala Harris was stumping elsewhere in Texas at the time. Biden himself hasn’t campaigned in Texas. Congressional candidate Wendy Davis, locked in a contentious race with freshman Rep. Chip Roy, R-Austin, was on board the bus but declined through an aide to discuss it.

“Rather than engage in productive conversation about the drastically different visions that Joe Biden and Donald Trump have for our country, Trump supporters in Texas instead decided to put our staff, surrogates, supporters, and others in harm’s way,” said Tariq Thowfeek, spokesman for the Biden campaign in Texas. “To the Texans who disrupted our events: We’ll see you on Nov. 3."

Trump’s instigations

Rather than condemning violence conducted in his name, Trump’s instinct has been to endorse it — sometimes with a wink, sometimes with more.

During the 2016 election, he offered to pay the legal fees of anyone who punched protesters at his rallies. At the first presidential debate against Biden, he said the white nationalist Proud Boys should “stand by” for post-election violence.

During the 2016 campaign, he insinuated that only assassination could stop Hillary Clinton if she were to win.

“If she gets to pick her judges, nothing you can do, folks,” he told a crowd in Wilmington, N.C. “Although the Second Amendment people — maybe there is, I don’t know.”

Trump insists that he’s been misunderstood when he’s accused of inciting violence, which happens with some frequency.

In a July 2017 speech to law enforcement, he condoned rough handling of suspects.

“When you see these thugs being thrown into the back of a paddy wagon, you just seen them thrown in, rough. I said, ‘Please don’t be too nice,’” he said.

“When you guys put somebody in the car and you’re protecting their head you know, the way you put their hand over [their head],” Trump continued, mimicking the motion. “Like, ‘Don’t hit their head and they’ve just killed somebody, don’t hit their head.’ I said, ‘You can take the hand away, OK?’”

The White House press secretary at the time, Sarah Huckabee Sanders, brushed it off, saying, “He was making a joke.”

Shortly before the 2018 midterms, Trump led a rally in Montana for Rep. Greg Gianforte, who had slammed a reporter to the ground during his campaign the previous year and later pleaded guilty to assault. “Any guy that can do a body slam, he is my type!” Trump told the crowd, eliciting cheers.

When George Floyd died under the knee of a Minneapolis police officer last May, and protests erupted nationwide, Trump threatened to send in troops and tweeted that “when the looting starts the shooting starts.”

In April, as Trump chafed at state public health measures aimed at blunting the COVID-19 pandemic, he urged gun owners in Michigan, Minnesota and Virginia to “liberate” their states from shutdown orders.

“LIBERATE VIRGINIA, and save your great 2nd Amendment. It is under siege!” he tweeted.

Right wing conspiracy peddlers have fed their audiences fearmongering about the political left and a coming civil war.

“They’ve been building a network of street activists since 2008, and the plan is to unleash them on Nov. 3,” Glenn Beck warned recently.

The day of the first Trump-Biden debate, Sept. 29, the FBI’s Dallas field office warned local law enforcement that the upcoming election could serve as a “potential flash point” for violence, according to The Nation, which obtained the advisory. In particular, the FBI warned about a rising threat from the rightwing “boogaloo” movement, extremist groups that call for a second Civil War.

The bulletin included photos of heavily armed men in tactical gear, from the social media account of one subject of an FBI investigation. The men referred to themselves as a QRF — military jargon for Quick Reaction Force.

No one hurt

Ahead of the bus incident, Donald Trump Jr. posted a video online urging his dad’s supporters to form a “Trump Train” to welcome Harris to Texas.

“It’d be great if you guys all get together … and give Kamala Harris a nice Trump Train welcome. Get out there, have some fun, enjoy it.”

Social media filled with footage from witnesses and participants. No one was hurt in the bus incident.

“They’re like literally escorting him out of town … This is the funniest thing I’ve ever seen,” tweeted one pro-Trump driver who recorded the caravan.

Video posted by another Trump supporter showed a black pickup just behind the Biden bus swerving out of its lane and swiping a white car with Biden campaign staff inside. The pickup driver identified himself on social media: Eliazar Cisneros.

In early September, Cisneros slowly drove the same truck through a crowd of protesters in San Antonio, using an expletive. No one was hurt, though protesters said they felt that was his intention.

Cisneros told KENS-TV in San Antonio at the time that he hadn’t been looking for trouble, just driving around, “waving my flags and showing support for my president …. I didn’t want to hurt anybody. You know, get off the street, get on the sidewalk and protest whatever you are protesting on the sidewalk.”

In early June, San Antonio’s WOAI-TV found Cisneros “patrolling” downtown San Antonio during protests after Floyd’s death, an assault-style gun slung over his shoulder. He said he wouldn’t use it only in response to vandalism, “but once bricks start flying or being threatened with our lives, yeah.”

State Rep. Terry Canales, D-Edinburg, wrote the director of the Texas Department of Public Safety, Steven McGraw, on Sunday to demand an investigation, in particular of the driver who swerved.

“Without a shadow of a doubt, the driver of the truck committed an aggravated assault with a deadly weapon,” Canales wrote. “Truly, setting aside all politics, there is no excuse for this sort of criminal behavior in Texas.”

Cisneros could not be reached.

In Philadelphia, Biden said the confrontation tracked Donald Trump Jr.'s comments. He noted that a Trump caravan shut down the Garden State Parkway in New Jersey on Sunday.

“Folks, that’s not who we are. We are so much better than this,” he said.

Trump reveled in the buzz.

“Did anybody see the picture of that crazy bus driving down the highway? They’re surrounded by like hundreds of cars and they’re all Trump flags all over the place. What a group,” he said Saturday at a rally in Montoursville, Pa., as supporters hooted and jeered. “It’s like a hot thing. See that’s really No. 1 trending.”

The 26-second clip he shared on Twitter shows the Biden bus surrounded on all sides by trucks waving Trump banners. A soundtrack is overlaid: “Welcome to the Red Kingdom,” a heart pounding techno fight song for the Kansas City Chiefs football team. By Sunday evening, the clip had been viewed 12.6 million times.

By the end of early voting Friday night, more Texans had voted than in all of 2016. With so little time left in the campaign, none of this is likely to affect the outcome, said Salehyan, the UNT professor.

“I don’t think it’s had a chilling effect on the electorate” he said, but “if things like this continue, it’s a really dark day for our democracy.”