New Federal Elections Commission filings show that a pro-Trump super PAC funded in part by Peter Thiel paid more than $134,000 to a company helmed by Steve Bannon in the final weeks of the presidential campaign—a set-up the watchdog group Campaign Legal Center says may have been illegal.

The super PAC, called Make America Number 1, is bankrolled largely by Robert Mercer, a New York hedge-fund billionaire with a very low public profile. His daughter Rebekah has quickly become one of the conservative movement’s most powerful financial backers; she’s on the board of the Heritage Foundation and the Manhattan Institute, and helps fund a host of right-wing media projects. She is also a close and longtime associate of Bannon, who is now one of Trump’s top White House advisers.

Mercer is also one of the 16 members of the Trump transition team’s executive committee. And a GOP fundraising source told Politico that it “would be difficult to overstate Rebekah’s influence in Trump world right now.”

The Daily Beast reported in November that Glittering Steel, a film company with virtually no online presence, is essentially “a front for Bannon.” We also reported that watchdogs say the payments the Make America Number 1 super PAC made to Bannon’s group could have violated campaign-finance rules, potentially by paying Bannon’s salary so the campaign wouldn’t have to. The new filings show that the super PAC was paying Bannon’s company all the way up through Election Day.

Alexandra Preate, Bannon’s spokesperson, told The Daily Beast on Friday that Bannon took a leave of absence from all his businesses when he joined Trump’s campaign.

The latest FEC filings, which became public a few minutes before the turn of midnight Friday, show the super PAC paid Glittering Steel $134,500 four payments total, from Oct. 26 to Nov. 4.

The Campaign Legal Center, a nonpartisan campaign-finance watchdog group, has urged the FEC to investigate Make America Number 1’s payments to Bannon’s company. It wrote that the Make America Number 1 super PAC is “inextricably intertwined” with the campaign, and that the two entities may have engaged in illegal coordination.

The new filings also show that Peter Thiel, the Silicon Valley billionaire who covertly bankrolled Hulk Hogan’s lawsuit against Gawker, gave $1 million to the super PAC on Oct. 26, less than two weeks before Election Day. Thiel isn’t the PAC’s only controversial funder. Older FEC filings show that Erik Prince, of Blackwater infamy, gave the PAC $100,000 on Sept. 21 and $50,000 on Aug. 21. Trump recently named Prince’s sister, Betsy DeVos, as his nominee for secretary of Education.

Make America Number 1 played a major role in the 2016 campaign; before backing Trump, the PAC was called Keep the Promise 1, and it boosted Ted Cruz. Kellyanne Conway, who went on to become Trump’s campaign manager and is now one of his top advisers, worked for it during that time. Conway left the super PAC after Cruz’s loss, and David Bossie, who headed Citizens United, stepped in to helm it before he too joined the Trump campaign.

The Mercers’ role in 2016 presidential politics drew attention right from the start. And while they generously backed the top two Republican contenders, they have also used their ample cash to take on other GOPers—most prominently Sen. John McCain. Robert Mercer and his wife spent $200,000 to boost his long-shot, conspiracy-theorizing primary opponent, Kelli Ward. As a member of the Senate Permanent Subcommittee on Investigations, the senator ripped into Mercer’s hedge fund for allegedly dodging more than $6 billion in taxes, and McCain said he believed the Mercers helped his opponent as payback.

Regardless of whether their super PAC’s payments to Bannon’s company were legal or not, it’s clear the Mercers were among the most powerful players in the 2016 presidential election. With Trump in the White House, their clout will only grow.