A New York City police officer used his squad car loudspeaker to chant “Trump 2020” at passersby in Brooklyn. A uniformed police officer walked into an early voting station in Miami wearing a “TRUMP 2020” face mask. And the country’s biggest police labor union used a photo of a Philadelphia police officer holding a toddler to peddle the false narrative that police had rescued him from “complete lawlessness” amid the city’s protests while urging people to vote for President Trump to promote “law and order.”

The series of incidents in the final days of the presidential election have led some Democratic voters, activists and organizations that monitor extremist groups to raise concerns about the potential for political bias among the police officers and sheriff’s deputies tasked with safeguarding the 2020 vote.

Several vocal police unions have endorsed President Trump, there have been several reports of uniformed police officers expressing explicit preference for the president in public, and there have been complaints of coziness or bias shown by some officers toward armed right-wing groups and self-described militias. The incidents have added to an already heightened climate of tension across the country.

Trump, who has been trailing in polls and has repeatedly attacked the election’s integrity, called this summer for law enforcement officers to patrol voting sites, which raised the specter of tactics historically used to scare minority voters.

Current and former law enforcement officials say that during recent elections, police in many cases have tried to avoid polling places to not appear as an intimidating force for voters. But this year, with the potential for widespread unrest amid social justice protests and intense political tensions nationwide, police have done unusually extensive planning, with officials saying they are dispatching more officers than prior years given the fraught atmosphere.

In Florida, Pinellas County Sheriff Bob Gualtieri told reporters last week that his office had decided to position sheriff’s deputies at all five early voting sites — the opposite of his earlier plans to avoid them to prevent people from feeling “intimidated or uncomfortable” — after armed men who claimed to work for the Trump campaign showed up outside a voting precinct.

Gualtieri said he hopes the deputies’ presence up through the end of early voting on Nov. 2 will instead provide “a calming presence.”

But Gaultieri also defended the presence of armed men who had provoked the allegations of voter intimidation, saying they were licensed security who had done nothing illegal, and were “just standing there, minding their own business.” Some of the county’s Democratic constituents have accused Gualtieri — a Republican of rising national stature, who was appointed earlier this year to Trump’s Presidential Commission on Law Enforcement and Administration of Justice — of pro-Trump bias.

“In downtown St. Petersburg, every day, there are Trump supporters waving flags on all of the corners surrounding the polling place, and police regularly drive by to give them waves and thumbs up,” said Danny Robinson, whose Web and media company is across the street from City Hall, one of the Pinellas County polling stations. He said Trump supporters respond with shouts of “Back the blue!” to police via megaphones.

A spokesman for Gaultieri did not respond to a request for comment.

Robinson echoed the allegations made by protesters in other parts of the country throughout a summer of racial reckoning, when police officers were sometimes accused of having cozy relationships — and friendly exchanges — with right-wing counterprotesters or militia-styled groups. That experience now underpins much of the concern from liberals about police bias on Election Day, as the Trump campaign has called for a “Trump Army” to watch the polls for fraud.

“I think that, unfortunately, what we’ve seen over the past several months is that there is a friendly relationship that emerges between members of law enforcement and far-right militias or at least a perceived friendly relationship on the part of the far right,” said Cassie Miller, a senior research analyst at the Southern Poverty Law Center.

In one of the most noteworthy examples in recent months, Miller pointed to a friendly exchange, captured on video, between an armed White teenager, Kyle Rittenhouse, and police in Kenosha, Wis., minutes before Rittenhouse opened fire and killed two protesters in what his lawyers say was an act of self-defense. In the video, which surfaced after the shooting, a police officer offers Rittenhouse bottled water and thanks him for being there.

Law enforcement is not fundamentally apolitical — many law enforcement leaders are elected members of political parties or are appointed by political leaders — but they are sworn to protect people equally and without bias. As private U.S. citizens, they can vote and express political opinions, and many elected sheriffs nationwide are vocal about those opinions, especially their support for “law and order” policies or laws that are tough on immigration.

Trump, since his first run in 2016, has repeatedly garnered the endorsement of some of the country’s most contentious and politicized sheriffs and law enforcement union leaders, including former sheriffs Joe Arpaio of Maricopa County, Ariz., and David Clarke of Milwaukee County, Wis., who repeatedly stumped for Trump during his 2016 campaign, while they held office. Trump later pardoned Arpaio of a misdemeanor conviction for racial profiling.

The president has made his unwavering loyalty to the country’s embattled police departments a core component of his reelection campaign, particularly in the face of this summer’s protests, which Trump and his conservative allies have painted as anarchic, anti-American and fueled by Democratic rage.

The country’s largest police union — the Fraternal Order of Police — as well as the largest police union in New York City and the Chicago Fraternal Order of Police are among the many law enforcement unions that have endorsed Trump.

Michael McHale, the president of the National Association of Police Organizations, spoke at the Republican National Convention this year, calling Trump “the most pro-law enforcement president we’ve ever had.”

Endorsements also have come from several law enforcement unions in critical battleground states, including the leading police organization in Michigan, a state where monitoring groups like the SPLC fear that self-styled militias could seek to “protect” the polls on behalf of Trump.

Armed Michiganders gathered at the State Capitol — and entered, with their guns — to protest Democratic Gov. Gretchen Whitmer’s coronavirus-related orders earlier this year. Fears of violence on Election Day were heightened after the FBI infiltrated a group of self-described militia members who allegedly were plotting to kidnap her. One Michigan sheriff, Dar Leaf of Barry County, had appeared onstage in May with one of the alleged conspirators.

When the state government earlier this month sought to ban the open carry of firearms inside polling facilities, Michigan law enforcement organizations, along with several county sheriffs, promptly said they would not enforce it. A judge blocked that order after pro-gun groups challenged it; state officials are appealing.

Bob Kroll, president of the 900-member Minneapolis Police Federation, appeared with Trump at a rally last year, wearing a “Cops for Trump” shirt that the union sells on its website. Kroll said the Obama administration had stymied and oppressed police, but Trump had returned to letting cops do their job, putting “handcuffs on the criminals instead of us.”

Kroll this week relayed a request to the union from the Trump campaign, asking for 20 to 30 retired officers to serve as Election Day poll “challengers” in a “problem area” of Minneapolis, the Minneapolis Star Tribune reported.

The union’s apparent willingness to help the Trump campaign immediately drew criticism from the city’s police chief, state attorney general, secretary of state and others.

“We don’t necessarily want our Poll Challengers to look intimidating, they cannot carry a weapon in the polls due to state law,” Trump campaign attorney William Willingham wrote in the letter to the union. “We just want people who won’t be afraid in rough neighborhoods or intimidating situations.”

Kroll did not respond to requests for comment this week and Willingham declined to comment when reached Friday.

Thea McDonald, a spokesperson for the Trump campaign, said Willingham is a volunteer assisting in Minnesota and acted on his own accord: “Neither the Trump Campaign nor the RNC instructed him to send this email.”

But McDonald added that police must be able to act as citizens too.

“Retired police officers are members of their communities, and as such are well within their rights to participate and volunteer as rule-abiding poll watchers,” McDonald said.

According to local regulations, political parties can send one challenger to each precinct in Minnesota. The party designees must only carry a letter showing they are there on the party’s behalf, and they are supposed to stay six feet from any voter and challenge only the ballots of those they have direct, personal knowledge of not living in their precinct.

Minneapolis Police Chief Medaria Arradondo quickly issued a statement reminding officers that they have “taken a solemn oath to protect the constitutional rights of all without favor or bias.” He said that oath remains for officers whether are “on or off duty.”

Experts say law enforcement bias or even perceived bias is problematic during an election not just because voters for the opposite party might feel intimidated, but because it can serve to embolden armed extremist groups.

“That can be a really dangerous development, because these armed vigilantes then essentially feel that they have a green light to go impose order,” Miller said.

Craig B. Futterman, a University of Chicago law professor and director of the Civil Rights and Police Accountability Project, viewed Trump’s call for law enforcement officers to protect the polls as a dog whistle to racists and extreme actors on the right, who would rather not see minorities vote because they tend to align with Democrats.

There is “a long history of police in this country who have played an active role in voter suppression and voter intimidation, particularly of Black folks,” he said.

As protests against policing tactics and racial injustice swept the country this year, some local and federal law enforcement authorities, along with Trump, have focused their public commentary on cases of violence, looting or property damage. Trump and his allies have denounced the demonstrators as dangerous and out-of-control, particularly in cities they view as hostile to the president’s agenda, such as Portland, Ore., Chicago, New York, and Philadelphia.

During unrest after police fatally shot Walter Wallace Jr. in his west Philadelphia neighborhood Monday, the national Fraternal Order of Police used social media to share a tale of police rescuing a lost toddler from the protests there and described officers as “the only thing standing between order & anarchy” — echoing language it had used while backing Trump.

In fact, police had seized the boy from his car seat after smashing the windows on his mother’s car and violently arresting her, the woman’s lawyer says. The lawyer said she drove inadvertently onto a street where police were confronting protesters. The police union later took down the posts, saying it had “subsequently learned of conflicting accounts” about what happened.

In New York, Terence A. Monahan, chief of department for the city’s police force, said during a recent election briefing that officers could effectively conduct their duties without any political bias, describing them as “apolitical” once they put on their uniforms, even though the city’s largest police union had endorsed Trump. The NYPD will have uniformed officers at every “at every polling location,” to secure the election, Monahan said.

Days later, the department said it was opening an investigation and suspending an officer without pay after a viral online video captured the officer in Brooklyn using his squad car loudspeaker to promote the president and taunt onlookers.

“Trump 2020,” the officer says in the video. “You can put it on YouTube, put it on Facebook. Trump 2020.”

Dermot Shea, the New York police commissioner, posted on Twitter that the video was “one hundred percent unacceptable.”

Trump later weighed in, tweeting: “Get that great Officer back to work!”

Tom Hamburger and Matt Viser in Washington and Jared Goyette in Minneapolis contributed to this report.