Just a few years ago, Paul Ryan was the GOP’s nominee for Vice President and the face of the party’s attempt to rebrand longstanding policy ideas for the age of income inequality and economic populism. Now, the Speaker of the House may find himself on the wrong end of a brash, macho sea-change within the conservative movement.

Ryan has not joined the so-called “Never Trump” movement within the Republican establishment. But he made waves this week by saying he could not yet support Donald Trump even though the billionaire has locked up the Republican nomination for the presidency. “Saying we’re unified doesn’t in and of itself unify us,” Ryan said Thursday on CNN.

The comments initially seemed to be the first steps in a delicate dance to bring the establishment conservatives Ryan represents together with the populist surge that has embraced Trump’s hateful rhetoric and retrograde policy ideas about women, Muslims, immigrants, and racial minorities. The two men are set to meet in person on Thursday. But Ryan’s remarks may be opening up a bigger gulf within the GOP.

On Sunday, sometime Trump surrogate Sarah Palin promised to help defeat Ryan in his primary contest with a Wisconsin businessman named Paul Nehlen, who seems eager to embody the same simplistic aggrieved-white-man machismo that’s fueled Trump’s rise.

In a campaign video, he rides a motorcycle through Wisconsin scenery in a sleeveless shirt that shows off his tattoos. As he parks the bike, the camera cuts to a closeup of the woman riding in the rear seat grabbing his shoulder to steady herself as she dismounts the bike. He criticizes Ryan over the Trans-Pacific Partnership (TPP) global trade treaty, and challenges Ryan to “come back to Wisconsin and debate me man to man, face to face, on the realities of TPP. And if you don’t want to debate me, maybe we can arm wrestle.”

The video is titled “Truth Resurrection,” but its portrayal of Ryan as a supporter of the trade deal is false. Ryan’s been critical of the actual deal, but helped pass a separate measure called Trade Promotion Authority (TPA), a pro-forma congressional action that makes it easier for the executive branch to negotiate a proposed treaty that must still be ratified by Congress. Lawmakers have granted presidents that authority as a routine matter of course going back decades and across party lines. Ryan even hammered some unusual concessions to GOP ideology into this edition of TPA.

Nehlen’s campaign plays up his background as a businessman who has sometimes worked with companies that brought manufacturing jobs back to the U.S. from other countries. A profile by the right-wing website Conservative Review describes him as “an all-American private sector success story” who worked his way up from a blue-collar trade to running his own business. Nehlen echoes Trump’s nativist rhetoric about the need to build a wall along the U.S.-Mexico border, and criticizes Ryan for failing to block refugee resettlement efforts and funding for the DREAM Act.

Nehlen is one of several down-ticket Republicans who are openly embracing Trump even amid fears the nominee’s misogyny and racism will hurt the party.

A Ryan loss is improbable — he has nearly $8 million in campaign cash on hand, his approval numbers remain strong inside of Wisconsin, and the only poll indicating a Nehlen surge comes from a pro-Trump fake news site — but wouldn’t be completely without precedent. Speaker Tom Foley (D) lost a re-election campaign in 1994, and Majority Leader Eric Cantor (R) managed to fumble away his own primary election in 2014.

And many of the hard-right voices that have pushed the GOP further and further adrift from its traditional, establishment guiding lights in recent years seem lathered up about Nehlen. His campaign is attracting positive coverage from Breitbart and Gateway Pundit, and touts a formal endorsement from far-right pundit Michelle Malkin.