Members of the Oath Keepers walk on the street during protests in Ferguson, Mo., in August 2015, around the anniversary of the Michael Brown shooting. (Lucas Jackson/Reuters)

Amid growing concerns about possible violence and vote fraud on Election Day, the Oath Keepers, a national group of former military and law enforcement officers, has urged its members to “blend in” with voters and do “incognito intelligence gathering and crime spotting” at polling places across the country on Nov. 8.

“In particular, we are calling on our retired police officers, our military intelligence veterans, and our Special Warfare veterans (who are well trained in covert observation and intelligence gathering) to take the lead,” group leader Stewart Rhodes said in a “call to action” on the group’s website and in a YouTube video urging members to “help stop voter fraud.”

The Oath Keepers are officially nonpartisan, but their concerns clearly echo Republican presidential nominee Donald Trump’s warnings about a “rigged” election and his calls for his supporters to monitor polling places for evidence of fraud by supporters of Democratic rival Hillary Clinton.

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Noting recent undercover video shot by conservative activists, Rhodes, a Montana attorney and Army veteran, told his supporters he is worried about “criminal vote fraud on an industrial scale.”

“We are, indeed, most concerned about expected attempts at voter fraud by leftists, but we will spot, document and report any apparent attempt at vote fraud or voter intimidation by anyone, of whatever party,” he said.

The call to action advises members to follow all laws, not to engage in direct arguments or confrontations with anyone at polling places and to report any suspicious activity to police.

“Dress to blend with the crowd,” Rhodes wrote. “That may mean wearing a Bob Marley, pot leaf, tie-die peace symbol, or “Che” Guevara T-shirt … or it may mean wearing working-man Carhartt pants and a plaid shirt.”

A D.C.-based civil rights group, the Lawyers’ Committee for Civil Rights Under Law, said Thursday that it would ask the Department of Justice to investigate the Oath Keepers’ actions.

“What’s particularly disturbing here is that they are encouraging their members to go out covertly and not disclose their identities,” said Kristen Clarke, the group’s president. “We want elections where there is transparency and openness. This kind of rallying call stands to intimidate voters and could have a chilling effect on Election Day.”

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Half of likely voters say they are at least somewhat concerned about violence either on Election Day or after, according to a Suffolk University/USA Today poll conducted this month. One in five likely voters say they are very concerned, about the same number who said they were not terribly confident that the United States would “have a peaceful transfer of power after the election.”

Mark Pitcavage, who monitors extremism for the Anti-Defamation League, said that despite the calls for restraint from its members, stationing Oath Keepers at polling places was potentially dangerous in an election where tensions are already so high.

“With this election, everything is heightened,” he said. “Because it is so contentious and controversial, and because emotions and passions are so high right now, any sort of action like this has the potential to have a greater effect.”

Pitcavage said the presence of Oath Keepers, even if they follow the law, has the “potential for intimidation,” as well as the potential for “angry backlash” from voters who feel they are being unfairly targeted. “Everybody’s tense, everybody’s nervous, everybody’s fearful and or angry,” he said. “It’s not a good idea to add something to the fire.”

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Police have also expressed concerns about the potential for conflict.

“Our concern will be with anybody showing up outside of a polling place that someone might perceive as a safety issue, or intimidation,” said Peter Simpson, spokesman for the Portland, Ore., police. “We’re fully aware of the emotions in this election. We don’t support anything that’s going to put community members in fear, on Election Day or any other day.”

Steven Crawford, the police chief in Bozeman, Mont., said he had not been contacted by Oath Keepers about plans to monitor polling stations.

“As long as they don’t violate any laws and interfere with anybody exercising their right to vote, then I don’t have a problem with it,” Crawford said. “This is a very unusual election. … We’re very aware that emotions are running high. So it’s more of an awareness for us, but nothing that we’re being additionally alert for.”

The Oath Keepers, founded in 2009, claims to have tens of thousands of members, but the actual membership is probably “a few thousand,” said Pitcavage, who lists the group as an “antigovernment extremist” organization.

Members of the Oath Keepers have vowed to honor their military or police oath to “defend the Constitution against all enemies, foreign and domestic” for life. They interpret that to mean standing up, often armed, against any laws or government actions they believe to be unconstitutional.

Heavily armed Oath Keepers have participated in several high-profile actions in the past couple of years, most notably guarding buildings in Ferguson, Mo., following the 2014 police shooting death of Michael Brown.

The group also participated in an armed confrontation with federal officials in 2014 in Nevada over rancher Cliven Bundy’s refusal to pay fees to graze his cattle on federal land. It also sent armed members to 2015 standoffs against federal authorities in Oregon and Montana in disputes over mining rights on federal land.

On the YouTube video, Rhodes said: “We don’t want the bad guys to know that we’re out there. We want to them worry about whether or not they’re being watched.”

Gregory McWhirter, an Oath Keepers official from Montana, urged members on the YouTube video to “be friendly, be observant” and “operate within the law” by using cellphones to video any suspected illegal activity.

“If you start to see busloads of people get off at one poll, just to get off the bus at another poll, report that to your local law enforcement,” McWhirter said, urging members to also report if they “see someone walking around with stacks and stacks of mail-in ballots.”

As an example for his members of how not to behave, Rhodes cited a 2008 case in which two members of the New Black Panther Party were charged with voter intimidation outside a polling station in Philadelphia. Those charges were later dropped, which led to allegations by some critics of racial preference in the Justice Department under President Obama.

“All states have laws on what can and cannot be done in or near a polling place, such as carrying firearms, filming, wearing political T-shirts, campaign buttons, etc, and protesting within a certain distance,” he wrote. “Be extremely careful and scrupulous in your obedience to any and all rules, regulations, and laws regarding all activity in or near a polling place.”

He also urged members not to wear Oath Keepers logos or identify themselves as Oath Keepers, except to police officers.

“If you wear Oath Keepers gear, you can expect to be accused by partisan Democrat activists and the media (essentially the same thing) of attempted voter intimidation …” he wrote. “Do not make it easy for leftist partisans to attempt to twist this around on you and on this org.”