WASHINGTON (AP) — Federal and state law enforcement officials have begun expanded preparations for the possibility of widespread unrest at the polls on Election Day, a response to extraordinarily high tensions among voters and anxieties about safety stoked in part by President Donald Trump.

FBI and local officials in several states have been conducting drills, running through worse-case scenarios, setting up command centers to improve coordination on reports of violence and voter intimidation, and issuing public warnings that any crime that threatens the sanctity of a Nov. 3 vote will not be tolerated.

The efforts are broader and more public-facing than in past years as fears grow over the potential for violent clashes in cities across the United States. Law enforcement officials say they are not responding to any specific threats or information but are preparing for a host of different scenarios that could play out.

Tensions are especially high given the increased political polarization and months of mass demonstrations against racial injustice that have seen violence by the left and right. Gun sales are way up. Six men were arrested after federal officials said they plotted to kidnap Gov. Gretchen Whitmer, D-Mich., at her vacation home. Experts are concerned that right-wing extremists will be emboldened by Trump's recent refusal to clearly denounce the Proud Boys, a neo-fascist group, and instead tell them to "stand back and stand by."

Trump has spent months suggesting without evidence that the election could be rigged. His call to supporters to "go into the polls and watch very carefully" has election officials worried about that unofficial or self-appointed "monitors" could chaos and conflict at voting places.

An FBI official said the agency was considering the current climate of the country in its preparations to ensure safety at the polls, as well as working with other agencies to protect the voting system. The official would not discuss the plans publicly and spoke to The Associated Press on condition of anonymity.

Adding to the alarm is the fact this election will be the first in nearly 40 years in which the Republican National Committee isn't barred from coordinated poll-monitoring activities. Democrats fear that could open the door to voter intimidation, the reason the courts have largely prohibited Republicans from poll monitoring since the early 1980s.

So far, experts who study extremism say they haven't seen any open discussion online of plans to instigate violence or interfere with voting.

Elon University professor Megan Squire, a computer scientist who studies online extremism, said the far-right extremists she tracks on social media appear to be preparing for trouble — a "prepper mindset" — without citing specifics.

"They're waiting for something to pop off," she said. "It's like a simmering kind of feeling."

She said the mindset is particularly keen among boogaloo supporters, a loose, anti-government, pro-gun extremist online network. Boogaloo adherents have shown up at protests against COVID-19 lockdown orders and protests over racial injustice, carrying rifles and wearing tactical gear.

In one of the internet forums Squire follows, a boogaloo supporter recently discussed plans to stock up on water, food, gasoline and generators in case "infrastructure goes down and supply lines are cut off."

Squire also said the Proud Boys, a group known for inciting street violence at rallies in the Pacific Northwest and elsewhere, appear to be emboldened by Trump's comments, as do less organized and strident figures posting on Facebook.

The deadly shooting by a heavily armed teenager during a protest in Kenosha, Wisconsin, in August has fueled "pro-vigilantism" attitudes among more mainstream conservatives, Squire said.

The Justice Department's civil rights division is responsible for enforcing federal voting rights laws and tasks U.S. attorney's offices with appointing special election coordinators to handle voting rights cases. The federal government has for decades sent prosecutors and federal observers to polling places to ensure compliance with federal law.

Local offices from New Mexico to Florida have been prepping, holding tabletop exercises and pouring over potential security threats.

But their jobs are especially fraught this year in part over concerns of politicization. Attorney General William Barr has repeatedly suggested without evidence that could be widespread mail-in voter fraud, though there is little to back that up.

This year, officials from a number of federal law enforcement agencies will be coordinating on Election Day at the FBI's Strategic Information and Operations Center, a global command center at FBI headquarters, people familiar with the matter said.

Justice Department prosecutors from different parts of the agency, including the civil rights and national security divisions, will be on hand to monitor incidents and help coordinate a federal response in the event of violence and threats to election infrastructure or cyberattacks, as well as high-profile incidents at polling places, said the people, who were not authorized to discuss the matter publicly and spoke on condition of anonymity.

The Justice Department and Homeland Security Department have sent additional personnel to cities where violence has cropped up during protests. The National Guard has designated military police units in Arizona and Alabama to serve as rapid reaction forces so they can respond quickly to any potential unrest.

But the first line of response on Election Day will be local law enforcement.

Philadelphia District Attorney Larry Krasner has launched a hotline that rings directly to assistant district attorneys, who will send detectives to investigate reports of voter suppression or intimidation. He said this week his office will not allow armed groups at the city's polling places amid growing concerns about voter intimidation by vigilante groups aiming to "protect the election." Such groups have caused violence at demonstrations.

But Oren Segal, vice president of the Anti-Defamation League's Center on Extremism, said he has not seen any specific campaigns for groups intending to target polling stations.

"A lot of the chatter that you see is going to be hyperbole, and one of the things we don't want to do is amplify hyperbole," he said.

Segal said white supremacists often turn to violence "when they feel like their culture is being taken away," while militias "tend to get more antsy when they think their guns are being taken away." Now he sees a possible threat from a loose coalition of vigilantes and other armed extremists who "think that their election is going to be taken away."

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Kunzleman reported from College Park, Maryland. Associated Press writers Claudia Lauer in Philadelphia and Eric Tucker contributed to this report.