President Trump’s debate-stage call for volunteers to stand watch at voting locations has prompted an enthusiastic response from known neo-Nazis and right-wing activists, leading many state election and law enforcement officials to prepare for voter intimidation, arrests and even violence on Election Day.

In his debate Tuesday night with Democratic presidential nominee Joe Biden, Trump did not explicitly condemn white supremacists or armed right-wing groups when asked to do so, and he falsely accused election officials in Philadelphia of improperly keeping poll watchers out of voting locations this week. The president provoked particular outrage when he was asked to condemn the Proud Boys, an all-male group associated with street violence, but instead said its members should “stand back and stand by.”

The Trump campaign and Republican National Committee for months have promised to recruit as many as 50,000 poll watchers to monitor voting locations on Election Day. The campaign’s “Army for Trump” website has contributed to that effort, urging supporters to join the “army of supporters fighting to re-elect him in 2020.”

But more-extremist supporters appeared to be joining that effort Wednesday, raising the prospect for confrontation and intimidation at polling locations.

“I got shivers,” Andrew Anglin, the founder of the neo-Nazi website the Daily Stormer, wrote in a post Wednesday. “I still have shivers. He is telling the people to stand by. As in: Get ready for war.”

Members of the Proud Boys repeated Trump’s false claims about election fraud in Philadelphia. The Official Michigan Proud Boys account posted a new logo on the encrypted messaging service Telegram based on Trump’s phrase: “Stand Back and Stand By” and reposted his tweet: “Must have a fair Election.”

Asked Wednesday about white supremacy, Trump told reporters that he had “always denounced any form of any of that.” He said he did not know who the Proud Boys were, and he tried to clarify his remarks from the previous evening: “They have to stand down and let law enforcement do their work.” Separately Wednesday, the president was asked whether armed, right-wing groups on street corners concern him. “Yeah, it does concern me, and crime generally concerns me,” Trump replied. “Any form of crime. And let law enforcement take care of it.”

Still, numerous civil rights leaders and Democratic lawyers said Trump’s comments could lead to illegal election interference, and several state attorneys general said they were preparing to arrest anyone who tries to prevent voters from exercising their rights.

“This is a blatant attempt at voter intimidation,” said Massachusetts Attorney General Maura Healey (D). “It’s very important to be clear about that. It’s illegal. It is a crime to engage in voter intimidation or election interference.”

A Trump campaign spokeswoman said in a statement that the president is encouraging his supporters to lawfully watch the polls because of a belief that Democrats will try to steal the election.

“Poll watchers are critical to ensuring the fairness of any election, and President Trump’s volunteer poll watchers will be trained to ensure all rules are applied equally, all valid ballots are counted, and all Democrat rule breaking is called out,” campaign spokeswoman Thea McDonald said. “And if fouls are called, the Trump campaign will go to court to enforce the laws, as rightfully written by state legislatures, to protect every voter’s right to vote. President Trump and his team will be ready to make sure polls are run correctly, securely, and transparently as we work to deliver the free and fair election Americans deserve.”

In an interview, Proud Boys leader Enrique Tarrio strongly denied any connection with white supremacists. “We weren’t planning on doing anything but canvass for the rest of the month,” he said about the group.

In most states, poll monitors must be registered with state authorities and are entitled to watch proceedings such as ballot counting only as representative of a political campaign or a party with standing in the election.

The Trump campaign dismissed accusations that it is inciting intimidation as partisan nonsense.

“The President’s campaign, like all Democrat and Republican campaigns, are recruiting election workers and observers to help out on Election Day,” senior adviser Justin Clark said in a statement. “This isn’t about intimidation but about transparency in the election process. Anything to the contrary is just demagoguery.”

Republican National Committee counsel Justin Riemer said in an interview that the party’s poll-watcher program is not an attempt at intimidation. He said the party targets polling places with a history of long lines and other problems that warrant observation. An RNC spokesman said poll watchers should follow all state and local laws about guns and would be trained to interact politely with voters and poll workers.

“We are very sensitive to those allegations that poll watchers are out there to stop people from voting,” Reimer said. “That is not why we are there. We make very clear to our volunteers. You need to be respectful, you need to be polite. You’re not there to be intimidating.”

Mark Krasovic, a historian at Rutgers University at Newark, said loosely organized groups may see license in the rhetoric of the president and his supporters, “whether they’ve been officially deputized to carry out this activity or not.”

The Oath Keepers, a militia group that formed more than a decade ago that comprises current and former law enforcement and military members, also has pledged to have “volunteer security teams” at Trump rallies and out on Election Day. The group was recently banned from Twitter.

Trump’s comments at the debate were “appalling,” and they are “setting the stage for election violence,” said Lindsay Schubiner, the program director at the Western States Center, a Portland, Ore.-based organization that tracks extremist groups.

“His statements really functioned as a rallying cry for the alt-right paramilitary group the Proud Boys, and they certainly interpreted it as such,” Schubiner said. “In the current context, it’s hard to interpret that as anything other than a call for voter intimidation.”

At least three Democratic attorneys general — in Massachusetts, Virginia and Nevada — have issued statements reminding the public that voter intimidation is illegal and that the law be enforced.

“There are ways that you can become a legitimate poll watcher,” said Nevada Attorney General Aaron Ford. “It requires certain attestations, and you are disallowed from intimidating or engaging with those who are voting.”

Already, instances of suspected intimidation have popped up at early-voting locations. On Sept. 19, the second day of early voting in the Virginia suburbs of D.C., Trump supporters staged a rally outside a polling place, requiring voters to make their way past the crowd and prompting accusations of impropriety. Republican officials said the pro-Trump group was not intimidating anyone and complied with the requests of election officials, the New York Times reported.

And in Philadelphia this week, at least one Trump supporter showed up at an election office to watch voters fill out absentee ballots and turn them in but was turned away. Trump alluded to the incident during Tuesday’s debate, falsely claiming that Philadelphia election officials were trying to hide fraud. Like most states, Pennsylvania requires poll watchers to be registered and to represent a campaign or political party.

“They went in to watch,” Trump said during the debate. “They were called poll watchers — a very safe, very nice thing. They were thrown out. They weren’t allowed to watch. You know why? Because bad things happen in Philadelphia, bad things.”

The effort to recruit volunteers nationwide who are prepared to contest voting eligibility, oversee counting and challenge results has reverberated in extremist corners of the Internet, where support for the president goes hand-in-hand with faith in debunked ideas about the “deep state” and a globalist, Satan-worshipping cabal.

Days before Trump used his debate platform to urge his supporters to stand watch at the polls, Albert Maimone, a 41-year-old devotee of the president in Westfield, Mass., posted a link to the “Army for Trump” website in a Facebook group for adherents of QAnon, the baseless conspiracy theory identified by the FBI as a potential domestic terrorism threat. Facebook said it was reviewing the QAnon content for violations of its policies.

Maimone, a Massachusetts Republican, is preparing to answer the call to show up at the polls.

“Yeah, we’re going to go to the polls,” the former chef said in an interview. “We’re going to go to the polls, and we’re going to be poll workers, and we’re not going to be scared of antifa or Black Lives Matter, and we’re going to represent our country. Me, personally, I’m not going to back down from any of this complete dishonesty.”

Another user who posted the link in a QAnon Facebook group, who declined to give his location in an interview, pledged, “Patriots will be working in all areas as well as the post offices.”

Facebook has been a central vector for the dissemination of conspiratorial, and frequently false, information about voter fraud and malfeasance at the polls, despite the company’s efforts to crack down on extremist groups and curb election-related misinformation.

Adding to the potential for violence is a robust militia infrastructure in numerous battleground states, according to analysts and academics tracking potential election-related conflagrations.

Michigan in particular could be a tinderbox, because of residual tensions from protests over pandemic restrictions, according to research conducted by Alethea Group and the Global Disinformation Index, two organizations tracking online threats. Lisa Kaplan, Alethea’s founder, said she and her team identified 25 militia groups in Michigan, including several that operate well-organized bureaucracies, including features such as organizational hierarchies, local chapters, and fitness and training activities.

Michael Lackomar, a communications officer and team leader for the Southeast Michigan Volunteer Militia, said several of his members are acting as poll watchers in their own communities. The group as a whole has no plans for widespread action but is “ready to respond to any violence that may spring up, or if the need arises to get some of our members out in more hostile areas.”

“No matter who wins in November, the other side is going to scream fraud,” Lackomar said. “I do not see a way for this to go quietly.”

Earlier this year, Trump floated the idea of using law enforcement officers to patrol polling places, invoking tactics historically used to intimidate voters of color.

“We’re going to have everything,” the president told Fox News host Sean Hannity in August. “We’re going to have sheriffs, and we’re going to have law enforcement, and we’re going to hopefully have U.S. attorneys and we’re going to have everybody, and attorney generals.”

The president has limited authority to order law enforcement to patrol polling places. Sheriff’s deputies and police officers are commanded at the local level, and a federal law bars U.S. government officials from sending “armed men” to the vicinity of polling places.

Ricky Hatch, who chairs the election committee at the National Association of Counties, said every election official in the country is wrestling with how to preserve the bedrock principle of open elections, which authorizes observers, while limiting the potential for chaos and conflict that could result from attempted interference with the tabulation process.

“We certainly don’t mind the observation, and the increased observation,” said Hatch, the clerk and auditor in Weber County, Utah. “We know that’s going to be higher in a high-stakes election like this. We just ask them to come with an open mind.”

Michelle Ye Hee Lee contributed to this report.