Meet President Trump’s favorite cop: an African American, cowboy hat-wearing, God-fearing conservative who stands for election as a Democrat, likens Black Lives Matter to the KKK, and has a habit of threatening violence against his critics on Facebook.

David Clarke Jr, sheriff of Milwaukee County in Wisconsin, is a local law enforcement leader who carries a national punch. Last year he toured the country as a Trump surrogate and was one of few black speakers at the Republican national convention; today, he regularly airs his provocative views on race and policing on Fox News. Sean Hannity, writing in a foreword to Clarke’s new book, Cop Under Fire, calls him “America’s sheriff”.

Now Clarke, a self-described “Trumpster”, is on a new mission. He plans to turn part of his 800-officer strong department into an immigration detection force so that he can help to execute one of the president’s most controversial and fearsome projects: rounding up and deporting millions of undocumented migrants.

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“I feel I have an obligation,” Clarke said in a two-hour interview with the Guardian in his Milwaukee sheriff’s office. “Otherwise I’m aiding and abetting. Criminal illegal alien crime is a problem in this country.”

Trump needs the extra muscle that local sheriffs and police chiefs can bring if he is to have any chance of implementing his controversial mass deportation plan. “They have to have the help of local law enforcement or they really can’t get this done,” Clarke said. “Everyone who is arrested for a misdemeanor or felony has to go through my jail.”

So last week, Trump’s favorite cop formally applied to join 287(g), the national system that delegates power from the federal immigration agency, Ice, to law enforcement departments. Under the program, Clarke would assign an as yet unspecified number of his 500 corrections officers at the county jail and 300 field patrol deputies to be trained by Ice in apprehending people for deportation.

At the end of a four-week training course in South Carolina, Clarke’s officers would be vested with the full authority of the federal government to check the citizenship status of anyone they stop and question, potentially turning individuals found to be in the US without permission over to Ice for removal. That’s a formidable capability that the Obama administration largely withheld from police officers to avoid blurring the lines between policing and immigration enforcement.

Facebook Twitter Pinterest Donald Trump talks with Sheriff David Clarke Jr in Milwaukee on 16 August 2016. Photograph: Eric Thayer/Reuters

Under Obama, Clarke said, “there were instances where we’d do a traffic stop, and there’s a sense that the guy was maybe in the country illegally, not just because he’s Latino – he doesn’t have a licence, doesn’t speak the language – pretty good chance, right? But we couldn’t ask about it or do anything about it.”

Under 287(g), by contrast, “I can bring the guy in and start to do the questioning.”

The idea that sheriff’s deputies will soon be patrolling the streets of Milwaukee acting in effect as Ice agents has sent a chill across the Hispanic community, which accounts for about 9% of the county’s almost 1 million population and the lion’s share of undocumented residents. It’s one thing for Ice agents to come pounding on your door in the middle of the night; it’s quite another to know that cops could stop you at any time and ask for your papers simply, critics say, because you look Latino.

“Racial profiling of Latinos is already happening and this will embolden people with prejudices to act on them,” said Christine Neumann-Ortiz of Voces de la Frontera, a Milwaukee-based community group that is leading protests against Clarke’s immigration plans. “Anyone who is booked through the county jail for something as trivial as driving without a license could find themselves put straight into deportation proceedings.”

Clarke dismissed the racial profiling argument. “Let’s define what we profile: we profile criminal behavior, not ethnicity. This term ‘racial profiling’ is thrown out there as flame-throwing – call them racist! – I’m not afraid of that crap.”

According to the sheriff, the aim of 287(g) is to catch those undocumented immigrants who have engaged in serious crimes. He gave the example of a Hispanic man who was picked up earlier this month for having threatened the suspect’s live-in partner and nine-year-old child with a knife and gun.

“This guy pulled a gun on his frickin’ kids. I want this guy gone. I never want to see him again – he’s a creep.”

Clarke reckoned that this case was just the tip of the iceberg within the Latino community. So how many immigrants without papers are there in Milwaukee County who have committed such serious crimes?

That’s a basic question that might be seen as the starting point of any discussion on whether the sheriff’s officers should be used in deportations. Yet when asked to give a number, he admitted he had no idea. “We can’t capture that, you’d have to get that from Ice,” he said.

Facebook Twitter Pinterest Sheriff David Clarke holds up a rifle that was presented to him as part of his Charlton Heston Courage Under Fire award at the 2015 CPAC convention. Photograph: Alex Brandon/AP

(Ice said it did not keep such data, and recommended that the Guardian contact local law enforcement – in other words, Sheriff Clarke – to “see what they might have handy”.)

The emphasis on “criminal aliens” is straight out of the Trump playbook. The president has frequently cited violent crimes committed by undocumented immigrants, most memorably the murder of Kate Steinle in San Francisco by a serially deported Mexican, as justification for his mass deportation plans.

But the argument is belied by the statistics. Numerous studies over many years have found that immigrants without legal status in the US commit fewer crimes overall than citizens.

Hispanic groups fear that it won’t stop with serious crimes, that anyone stopped by the sheriff’s deputies for even the most minor infractions – a broken car tail light, for instance – could find themselves flung into the deportation pipeline. “That’s Ice’s problem, I’m worried about the criminal illegal,” Clarke insisted.

But in his Guardian interview, the sheriff injected a note of ambiguity, suggesting that misdemeanors could be fair game. “I don’t think it’s too much to ask for someone in this country illegally to abide by all our laws – I don’t care what the crime is,” he says. “If I went to Mexico, I don’t get to engage in misdemeanor crimes and then say, ‘Well, it’s just a misdemeanor.’”

Clarke’s supporters liken him to a radio show shock jock, calling him a “black Rush Limbaugh with a badge”. His vitriolic style bears comparison – and he has been inundated with criticism from human rights groups since he announced his intention to join 287(g). The most personal attack that has been directed against the plan by political opponents and news outlets such as the local Milwaukee Journal Sentinel (he calls it the Urinal Sentinel) is that he is an absentee sheriff.

He is so focused on his national media profile, the argument goes, so desperate for a post in the Trump administration, that he has ceased to serve the people of his county. Why would he want to take on a whole new federal responsibility over immigration when he is failing to meet his existing obligations as sheriff?

“I’m insulted by that,” Clarke responded when the Guardian put that to him. “Maybe they think a black guy can’t do more than one thing at a time. It’s insulting.”

Facebook Twitter Pinterest Sheriff David Clarke Jr was one of the few black speakers at last year’s Republican national convention in Cleveland, despite having been elected as a Democrat. Photograph: Mike Segar/Reuters

His critics raise as evidence of his alleged neglect the incidence of no fewer than four inmate deaths at the Milwaukee County jail in the past year. One of the deaths, in which a 38-year-old with bipolar disorder died of dehydration after his water supply had been shut off for six days in response to his erratic behavior, was ruled a homicide.

Clarke called the storm over the jail deaths a “manufactured issue. This is a disguised political attack. Four deaths in a jail, yeah, OK, there were four deaths in a jail, not connected in any way. People die in hospitals, people die in nursing homes, people die – doesn’t mean we had anything to with it.”

But surely, people don’t die in hospital from dehydration?

“You cite one that might be problematic,” he conceded, adding that “this guy was in bad health. It was a contributing factor.”

Clarke has responded to the claim that he is an absentee sheriff forcefully on social media. When the Democratic mayor of Milwaukee, Tom Barrett, mocked him for “fightin’ crime one conservative cable TV show at a time”, Clarke used Facebook to recall a 2009 incident in which Barrett “got his ass kicked” as he tried to protect a grandmother who was being harassed at the state fair. Then Clarke threatened the mayor: “Time to crawl back into your hole Tom, unless you want some more of this because I have some.”

Facebook Twitter Pinterest A screen shot of the Milwaukee County sheriff’s Facebook page, including a quote from David Clarke. Photograph: @MilwaukeeCountySheriff/Facebook

The Facebook outburst was not isolated: Clarke is experienced in attacking opponents in openly pugilistic terms. At Trump’s inauguration celebrations in January, he told a crowd that the only time he’d reach across the aisle to work with liberals would be to “grab one of them by the throat”. An artist subsequently crafted a souvenir bobblehead toy portraying Clarke in his trademark cowboy hat with one hand saluting and the other reaching out for an opponent’s neck.

Facebook Twitter Pinterest A Sheriff David Clarke talking bobblehead is shown during the CPAC in Maryland in February. Photograph: The Washington Post/Getty Images

Clarke is currently being sued by a Milwaukee resident, Dan Black, who alleges that he abused his sheriff’s authority after they had an encounter in January onboard a flight from Dallas to Wisconsin. Black shook his head at Clarke in disapproval at the sheriff’s longtime support of the Dallas Cowboys football team rather than the Wisconsin team, the Green Bay Packers.

When they arrived back at Milwaukee airport, Black found himself detained, the lawsuit alleges, by six of the sheriff’s deputies, who questioned him for 15 minutes before escorting him from the airport. After Black complained, Clarke posted his picture on Facebook with the words: “Cheer up, snowflake … If Sheriff Clarke were to really harass you, you wouldn’t be around to whine about it.”

Facebook Twitter Pinterest Screen shot of the Milwaukee County Sheriff’s Facebook page including a quote from Sheriff David Clarke. Photograph: @MilwaukeeCountySheriff/Facebook

Clarke told the Guardian he couldn’t comment on the lawsuit as it was the subject of litigation, though he did add: “Let me say this, frivolous lawsuit. This guy’s looking for 15 minutes of fame, that’s what it’s about.”

There’s something odd about the way Clarke deploys such violent language against his adversaries. He is, after all, a law enforcement leader and a staunch “law-and-order” guy who was in the running for the post of homeland security secretary and is still in contact, he said, with the Trump administration.

“I play smash-mouth politics,” he says. “Politics is a contact sport. I didn’t create the rules. It’s hit or be hit. I understand the environment. People are trying to slit my throat politically and personally, so you better be ready when they come after you.”

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There’s also an ambiguity to much that he says, such as his notorious tweet during the election in which he said it was “pitchforks and torches time”. Was it a twisted joke, a metaphor for political activism, or a literal call to arms?

“I’ll leave that to the reader,” he says. “People will say, ‘Pitchforks! Oh, he’s advocating violence!’ No, I’m not. But I won’t take it back or apologise.”

Despite his denials, such high-testosterone talk adds to the jitters around his intention of joining 287(g). If this is what he is like now, his detractors argue, how will he be when he gets his hands on immigration powers as well?

“Our position is, he is someone who is dangerous and reckless, he shouldn’t be given any more authority,” said Neumann-Ortiz.

Trump’s favourite cop, who has won four sheriff’s elections since 2002, each time running as a Democrat and each time gaining almost 80% of the vote, is utterly unfazed. “The voters will decide whether they like it or not, not the pro-immigration folks who are on me all the time. I don’t care about the pressure and the politics – I took an oath and I’m going to do my job.”