Nehlen is a Wisconsin executive who touts his work bringing jobs back to the United States from Mexico and Canada, a key asset in the manufacturing-heavy Wisconsin district that Ryan represents. And he's gotten the highly vocal support of conservative activists like Sarah Palin and Michelle Malkin.
But it still appears to be a steep climb for anyone looking to unseat Ryan, who is highly popular in Wisconsin and bested his last primary challenger 94%-6% in 2014.
But Palin promised she would get on board any effort to topple Ryan after he expressed his hesitation with presumptive Republican nominee Donald Trump last week. Palin, who has been a vociferous surrogate for Trump and mentioned as a possible running mate, promised that Ryan would be "Cantored"
"His political career is over but for a miracle because he has so disrespected the will of the people," Palin told CNN's Jake Tapper on "State of the Union" on Sunday.
The stunning defeat of then-House Majority Leader Cantor to a little-known primary challenger has become an allegory in Washington for incumbents who might otherwise brush off seeming longshots.
But Ryan appears highly unlikely to suffer the same fate -- he's well-liked by most Wisconsin Republicans and has been a regular presence in his home district.
"The bottom line is you look at Cantor and say, 'Could it happen?' Well, I suppose it could happen. But there's not the early warning signs that you look for," said Charles Franklin, a veteran Wisconsin pollster at Marquette University.
Ryan's favorability among Wisconsin Republicans has been consistently above 70%, Franklin said, and is close to 80% in the Milwaukee media market -- which includes almost all of Ryan's congressional district.
Ryan's office said that his constituents know Ryan and "what he stands for."
"People in southern Wisconsin know Paul Ryan, and they know what he stands for," Ryan spokesman Zack Roday said in an email. "Janesville is his home, and his commitment will always be to the people he represents."
Nehlen said last month that he was challenging Ryan for his support of fast-tracking the Trans-Pacific Partnership trade agreement and that he was willing to spend a "substantial amount" of his own money.
"This is clearly a David-and-Goliath fight. Paul Ryan has over $5 million in his campaign chest," Nehlen told CNN's Manu Raju. "He's an 18-year establishment career politician, quite honestly, but we've seen the big fall before. Eric Cantor lost in Virginia's 7th District; Paul Ryan is going to fall just as hard or even harder."
The focus on manufacturing jobs and trade pacts makes sense in Wisconsin's 1st District, which runs along the southeast border with Illinois and includes former automaker towns like Janesville and Racine.
But if Nehlen is going to win, it's unlikely to be with the help of Trump supporters. Ted Cruz won the Republican presidential primary in the district with 50.7% of the vote, followed by Trump with 32.2% and John Kasich with 14.6%.
The promise from Palin to campaign for Nehlen adds to some of the star power he has garnered recently. Nehlen is also hosting a fundraiser with conservative activist Malkin later this month.
But it's unclear whether even Palin can sway Wisconsin Republicans. "I don't think she has a big following here that would make you think that her views would be especially influential in this race," Franklin said.