A week after President-elect Donald Trump’s victory, Elon Musk said his political action committee would “play a significant role in primaries.”

The following week, the billionaire responded to a report that he might fund challengers to GOP House members who don’t support Trump’s nominees. “How else? There is no other way,” Musk wrote on X, which he rebranded after purchasing Twitter and moving to boost conservative voices, including his own.

And during his recent visit to Capitol Hill, Musk and entrepreneur Vivek Ramaswamy delivered a warning to Republicans who don’t go along with their plans to slash spending as part of Trump’s proposed Department of Government Efficiency.

“Elon and Vivek talked about having a naughty list and a nice list for members of Congress and senators and how we vote and how we’re spending the American people’s money,” said Rep. Marjorie Taylor Greene, R-Ga.

Trump’s second term comes with the specter of the world’s richest man serving as his political enforcer. Within Trump’s team, there is a feeling that Musk not only supports Trump’s agenda and Cabinet appointments, but is intent on seeing them through to the point of pressuring Republicans who may be less devout.

One Trump adviser, speaking on condition of anonymity to discuss internal political dynamics, noted Musk had come to enjoy his role on the campaign and that he clearly had the resources to stay involved.

The adviser and others noted that Musk’s role is still taking shape. And Musk, once a supporter of President Barack Obama before moving to the right in recent years, is famously mercurial.

“I think he was really important for this election. Purchasing Twitter, truly making it a free speech platform, I think, was integral to this election, to the win that Donald Trump had,” said departing Republican National Committee co-chair Lara Trump, the president-elect’s daughter-in-law. “But I don’t know that ultimately he wants to be in politics. I think he considers himself to be someone on the outside.”

During the presidential campaign, Musk contributed roughly $200 million to America PAC, a super PAC aimed at reaching Trump voters online and in person in the seven most competitive states, which Trump swept. He also invested $20 million in a group called RBG PAC, which ran ads arguing Trump would not sign a national abortion ban even as the former president nominated three of the justices who overturned a federally guaranteed right to the procedure.

Musk’s donation to RBG PAC — a name that invokes the initials of former Supreme Court Justice Ruth Bader Ginsburg, a champion of abortion rights — wasn’t revealed until post-election campaign filings were made public Thursday.

Musk has said he hopes to keep America PAC funded and operating. Beyond that, he has used his X megaphone to suggest he is at least open to challenging less exuberant Trump supporters in Congress.

Another key Trump campaign ally has been more aggressive online. Conservative activist Charlie Kirk, whose group Turning Point Action also worked to turn out voters for Trump, named Republican senators he wants to target.

“This is not a joke, everybody. The funding is already being put together. Donors are calling like crazy. Primaries are going to be launched,” Kirk said on his podcast, singling out Sens. Joni Ernst of Iowa, Jim Risch of Idaho, Mike Rounds of South Dakota and Thom Tillis of North Carolina as potential targets. All four Republican senators’ seats are up in 2026.

For now, Musk has been enjoying the glow of his latest conquest, joining Trump for high-level meetings and galas at the soon-to-be president’s Mar-a-Lago resort home in Palm Beach, Florida. The incoming administration is seeded with Musk allies, including venture capitalist and former PayPal executive David Sacks serving as the “White House A.I. & Crypto Czar” and Jared Isaacman, a tech billionaire who bought a series of spaceflights from Musk’s SpaceX, named to lead NASA.

Musk could help reinforce Trump’s agenda immediately, some GOP strategists said, by using America PAC to pressure key Republicans. Likewise, Musk could begin targeting moderate Democrats in pivotal states and districts this spring, urging them to break with their party on key issues, Republican strategist Chris Pack said.

“Instead of using his influence to twist GOP arms when you have majorities in both houses, he could start going after Democrats who vote against Trump’s agenda in states where the election was a referendum for Trump,” said Pack, former communications director for the National Republican Senatorial Committee. “Otherwise, if you pressure Republicans with a primary, you can end up with a Republican who can’t win, and then a Democrat in that seat.”