Thousands of Trump campaign supporters stepped up their public show of celebration, promotion and, in some cases, tacit intimidation over the weekend as a nervous nation prepared to head to the polls in two days.

The events, car caravans, midsize outdoor rallies and, on Sunday, the apparent blocking of roadways in the Democrat-heavy Mid-Atlantic, have been building in size as Election Day approaches. No injuries — or ostentatious displays of rifles and pistols — were reported, but the demonstrations underscore the unusual nature of this national election and the ends-justify-the-means tactics President Trump and his supporters often embrace.

In addition to the violent rhetoric and previous armed demonstrations by the far-right organization known as the Proud Boys, the election is being shaped by security precautions to prevent the spread of the novel coronavirus. More than 68 percent of the entire 2016 vote count already has been cast by mail and in person, a record that might help reduce long Election Day lines and the partisan frustrations that sometimes emerge.

But the early voting has been marred by accusations of voter intimidation and unease around the polls, including many reports of caravans of honking vehicles flying Trump flags at times blocking access to voting sites.

The FBI confirmed Nov. 1 it is investigating an incident in which a group of Trump supporters surrounded a Biden campaign bus on Interstate 35 in Texas. (The Washington Post)

Although the cases have drawn significant attention online and have circulated widely on social media, they often stop short of crossing the line into illegal voter intimidation, election experts and officials say. What constitutes voter intimidation can be “subtle and context-dependent,” according to the Institute for Constitutional Advocacy and Protection at the Georgetown University Law Center.

On Sunday, a group of Trump supporters in a vehicle caravan was filmed blocking the northbound express lanes of the Garden State Parkway in New Jersey. A man shooting video that was posted to Twitter can be heard saying, “We shut it down, baby. We shut it down.” The New Jersey State Police confirmed that the parkway was blocked but declined to provide additional information Sunday evening, saying authorities were still gathering details about what happened.

The highway stunt followed a similar, if more serious, one in Texas on Friday. Nearly 100 cars driven by Trump supporters surrounded a bus carrying Biden-Harris supporters due to appear at scheduled rallies, forcing it to a near stop; Biden-Harris proxies canceled the rest of the day’s events.

“They’re like chasing him out of the city,” one man said in a social media video, as “Eye of the Tiger” played in the background. “There’s like hundreds of them. They’re escorting them out.”

A woman says in another video: “We’re riding him out of Texas. It is hilarious.”

Long a deep if somewhat paling red, Texas might be in play this year, and a defeat in the Lone Star State would doom Trump’s reelection bid. Trump championed the public disruption in a tweet on Saturday, along with a picture of the cars surrounding the bus: “I LOVE TEXAS!”

On social media, members of the group that surrounded the bus — a chapter of an organization called the “Trump Train” — were alternately defending the legality of the action and boasting about their ability to run Joe Biden’s campaign out of their community.

Michelle Lee, a spokeswoman for the FBI’s San Antonio Field Office, confirmed Sunday that the FBI is “aware of the incident and investigating.” The FBI investigation was first reported by the Texas Tribune.

Trump has defended the group’s actions, posting Monday on Twitter that “They did nothing wrong.” he instead went on to decry what he called “the ANTIFA Anarchists, Rioters and Looters, who have caused so much harm and destruction in Democrat run cities,” saying that they were “being seriously looked at!”

Alarm about voter intimidation has grown in the run-up to Election Day, with civil rights advocates and election officials alike expressing concerns about voters who might feel frightened heading to the polls.

These anxieties appear particularly pronounced this year, with authorities, voters and experts also worried about possible unrest or violence Tuesday or in the days that follow.

Actions that amount to illegality include violent behavior in or outside polling places, confronting voters in official or military-style outfits, following voters, verbally threatening violence or aggressively asking people whether they are qualified to vote, the institute says.

Guns at polling sites also can be viewed as intimidating, though they also are legal in many cases. Citing fears of firearms intimidating voters, Michigan Secretary of State Jocelyn Benson (D) last month banned people from openly carrying guns at polling sites there on Election Day, but pro-gun groups challenged it in court, and a judge blocked the directive. The state is appealing.

Police say they are conducting unusually extensive election preparations, and departments across the country have emphasized they are protecting against possible voter intimidation, along with guarding against violence or clashes at the polls.

Some incidents of police showing clear backing for Trump — who has emphasized his support for law enforcement — have stirred additional fears among activists and others about possible bias among local officers who will be policing the polls.

They include a uniformed Miami police officer photographed wearing a Trump campaign-themed mask at a voting station and a New York police officer suspended after being filmed using his squad car loudspeaker to chant “Trump 2020” at people in Brooklyn.

In addition to repeatedly assailing the election’s integrity, Trump has sparked more unease about intimidation with his remarks, including his call for law enforcement officials to patrol voting sites, which raised the specter of tactics long used to frighten minorities.

During the first presidential debate, Trump said he was “urging my supporters to go into the polls and watch very carefully.” His campaign has defended volunteer poll watchers, who it said would be properly trained, and described observers as not “about intimidation but about transparency in the election process.”

Local and state officials have pushed back at Trump’s rhetoric regarding the election. In Philadelphia, a city that Trump has repeatedly singled out for criticism, District Attorney Larry Krasner issued a blistering statement last week against the president.

“Philadelphians from a diversity of political opinions believe strongly in the rule of law, in fair and free elections, and in a democratic system of government,” Krasner said. “We will not be cowed or ruled by a lawless, power-hungry despot.”

The Massachusetts Attorney General’s Office issued an advisory emphasizing that state and federal laws “prohibit private actors from engaging in voter intimidation,” describing that as including a wide range of actions, from verbal and physical confrontations to following voters or demanding documentation.

In New Hampshire, the attorney general and secretary of state sent out a memorandum with guidance on issues including intimidation, warning against anyone using force, violence or coercion. The memo also noted that state law makes it a felony for someone to use any force, threat or violence to force someone to vote a certain way or not vote at all.

“Voter suppression or intimidation is not tolerated in New Hampshire,” the memo stated.

Minnesota Attorney General Keith Ellison (D) said that a private security firm seeking former Special Operations personnel to guard polling places had canceled its plans, which he had described as something that could intimidate voters: “Minnesota and federal law are clear: It is strictly illegal to intimidate or interfere with voters.”

Much of the focus running up to in-person voting has centered on states where handguns and rifles have been displayed at political rallies — and, in one of those states, Michigan Gov. Gretchen Whitmer (D) was the target of an alleged kidnapping plot authorities say was planned by an armed right-wing group.

Lansing City Clerk Chris ­Swope, also president of the state’s municipal clerk’s association, said recent demonstrations at the Michigan Capitol have left many on edge. In late April, demonstrators protesting Whitmer’s pandemic restrictions noisily entered the capitol, flanked by heavily armed men in paramilitary gear.

“It’s always unnerving when there’s discussion of people showing up with guns at the polls,” Swope said. “I’ve got poll workers at polling locations expressing concerns to me about that.”

There are particular concerns in African American enclaves across the state, in places such as Flint and Benton Harbor, which are located in counties that are overwhelmingly White.

Flint City Clerk Inez Brown said Sunday that recent events had her worried that people might show up at polling places with guns to intimidate voters.

“Naturally, we’re concerned,” Brown said. “I hope and pray that nothing violent happens.”

John Gleason, who has served in public office in Genesee County for more than two decades and has been the county clerk since 2012, said he doesn’t know of any time that people have openly carried guns to the polls in Michigan. But he says the energy for it has blown up since Benson’s decree inflamed conservatives.

In Michigan, permit holders are not allowed to carry guns at schools and can carry them in churches only if they have permission from the pastor. Gleason said all of the voting locations in Genesee County effectively fall under those restrictions.

“When you challenge them gun nuts, when you challenge them, they’ll accept,” Gleason said. “Nobody wore guns to the polls, but as soon as she made it an issue, then the crackpots got to do their part. . . . I guarantee you now there will be open carry at the poll. It was not even an issue those three weeks ago.”

Arthur Woodson, a community activist in Flint, was taken aback when he saw news reports of the Biden bus being driven off the road in Texas and law enforcement breaking up a Black Lives Matter march to the polls in North Carolina.

“The bus reminded me of the freedom fighters down in Mississippi, where the three young men were murdered. And watching North Carolina, it reminded me of 1964, with Martin Luther King, when all of them was marching to vote,” Woodson, who is Black, said Sunday. “I was up all last night thinking about it.”

Speaking to a crowd in Washington, Mich., on Nov. 1, President Trump referenced supporters in Texas who allegedly tried to run a Biden bus off the road. (The Washington Post)

Much like Michigan, a magnet for showy partisan tensions before the election, Portland, Ore., also has seen flares of unrest in recent days.

On Saturday night, Portland police declared a riot after 150 demonstrators broke windows and threw objects at officers near the arena where the city’s NBA team plays, another in a series of conflicts between protesters and police that shows no sign of abating.

The Rose City has been the site of right-wing and left-wing protests this year. Demonstrators have taken to the streets almost nightly since George Floyd was killed in Minneapolis police custody in May.

The consistent conflagrations — often focused on downtown police headquarters and a federal building next door — have turned blocks of the city center into a maze of boarded-up buildings. Trump has said the city is the poster child for a lawless Democratic city.

A September rally by the Proud Boys ended without violence, but spasms of conflict between ideologically opposed groups have turned violent, even deadly.

Wilson reported from California, Berman reported from Washington, D.C., and Ruble reported from Michigan. Matt Zapotosky in Washington, Cleve J. Wootson in Portland, Ore., and Moriah Balingit and Tom Hamburger in Michigan contributed to this report.