A little-known businessman from Wisconsin has become a pawn in the drawn-out battle between Donald Trump and House Speaker Paul Ryan.

And by riding the wave of Trump’s implicit support, he’s hoping to knock out his high-profile opponent in next week’s primary.

The sudden spotlight on Ryan's primary challenger, Paul Nehlen, comes as the rift deepens between the Republican presidential nominee and party leaders who've been fending off criticism over Trump's off-brand behavior — the latest example being his unnecessary exchange with the parents of a Muslim-American U.S. Army captain killed in Iraq.

In this photo taken Thursday, May 19, 2016, in Kenosha, Wis. Paul Nehlen, a Republican, stands outside his campaign office. He plans to take on U.S. Rep. Paul Ryan, also a Republican, in the Aug. 9 primary. AP Photo/Carrie Antlfinger

Nehlen, while largely considered a long shot, is trying to use his new-found publicity to boot Ryan from his congressional seat — an upset that could signal whether Trump's personal political clout can move voters in November.

Nehlen received a flood of national attention this week when Trump first tweeted his thanks for defending him against Ryan. Trump followed up by telling The Washington Post on Tuesday that Nehlen’s "running a very good campaign" — while refusing to endorse Ryan.

"I like Paul, but these are horrible times for our country,” Trump said. “We need very strong leadership. We need very, very strong leadership. And I’m just not quite there yet. I’m not quite there yet.”

Those words echoed Ryan’s own refusal to back Trump in May, when he told CNN that "I’m just not ready to do that at this point. I’m not there right now."

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Ryan eventually came around and endorsed the real estate mogul — but Trump may see an opportunity for payback in stirring up interest in Nehlen.

The odds against Nehlen are considerable. He has little political experience, no prominent endorsements in the state and a deep fundraising disadvantage, with just $175,000 cash on hand as of July 20 to Ryan’s $9.5 million.

But there is precedent for such an upset. In 2014, a little-known, underfunded professor named Dave Brat rode a wave of anti-establishment sentiment and a handful of big-name conservative Republican endorsements to a stunning defeat of then-House Majority Leader Eric Cantor.

Brat enjoyed a burst of free media, sparked in part by fierce attack ads launched by Cantor and his allies, that helped raise his profile beyond a faceless name on the ballot on Election Day.

Now, Trump’s shout out to Nehlen is giving him the kind of free media attention most House candidates can only dream of, with the candidate doing interviews on local and national television all day Tuesday.

Like Brat, Nehlen boasts the support of some major conservative movement figures. Conservative commentator Michelle Malkin has endorsed him, Sarah Palin promised to work on his behalf to defeat Ryan (though that has yet to materialize in any substantial way), and Ann Coulter is set to join Nehlen for a campaign rally in Wisconsin this Saturday.

John Pudner, Brat’s main consultant on his race, said he sees the same the outsider vs. establishment themes playing out in Nehlen’s battle against Ryan, and noted that grassroots frustration helped overcome Cantor’s more seasoned political team.

“I think the fact that people are concerned this is kind of an insider process in D.C. is the reason you’re seeing a groundswell of attention and interest in his race,” he said.

It was energetic grassroots support fueled by an anti-establishment, populist wave that helped drive Trump to improbable primary wins in states where he lacked any infrastructure or local endorsers.

Nehlen has fashioned himself after Trump in both substance and style, hoping to ride that same wave to his own unlikely victory. In one of his ads, Nehlen carries a box labeled “drugs” across the border and declares, "Cheap Mexican heroin is killing Americans in record numbers, and it has got to stop,” adding Ryan has “failed” at addressing the problem.

But there’s a key difference between Nehlen and Brat: Paul Ryan isn’t Eric Cantor, and Wisconsin’s 1st district is different from Virginia’s 7th.

Ryan’s Wisconsin allies — and even some of his detractors — say he has made it a point throughout his ascent in national prominence to keep up his commitment and ties to his district. Where Cantor was seen as more focused on D.C. than his own district, Ryan has kept his family in his home district and required, as a prerequisite to becoming speaker, that he spend every weekend and as much of recess at home as possible.

“Unlike Cantor, he’s really in touch here. He’s very, very popular, his approval rating’s extremely high, he’s got a really good organization in the district,” said Charlie Sykes, a prominent Wisconsin talk-radio host and frequent critic of Trump.

Pudner said he was impressed by the fact that Ryan appeared at the state party convention, and seemed very accessible. Where Ryan's received endorsements from all of the district's 16 state legislators, Nehlen’s prominent endorsers, Sykes noted, are all from outside the state

Notably, he and the rest of the district’s influential conservative talk-radio hosts have either stayed out of the primary or been friendly toward Ryan. It was talk-radio opposition that helped doom Trump in the primary there.

And that may be the biggest challenge Nehlen has, as Trump increasingly puts his thumb on the scale of the race: Wisconsin’s 1st district is not Trump Country.

It’s far more moderate than Brat’s, which runs from the Washington, D.C., suburbs down to Richmond, Virginia. Trump lost the district to Ted Cruz by 19 points, and the suburban collar counties hold exactly the well-educated white Republican voters that Trump has struggled to attract.

That could offer Nehlen an opportunity. The state’s open primaries mean Democrats and independents can vote in Ryan’s primary next week, and Nehlen’s campaign has been careful to focus on tying Ryan to Hillary Clinton and Barack Obama, rather than Trump alone, in his recent statements, a clear attempt to attract disillusioned moderates and Democrats.

But with Trump campaigning in Wisconsin on Friday, it will be difficult for Nehlen to hold the candidate at arms’ length. And as Brandon Scholz, a Wisconsin GOP lobbyist and former state party executive director, said in an interview, “the Trump thing is not an opening.” He said the Trump campaign isn’t well-organized in the district, so even if there was a groundswell of Trump support for Nehlen, there’s no apparatus to turn it out.

“Trump didn’t do well in that district. There are some Trumpkins there, but not enough,” he said.