A campaign watchdog group filed a complaint with federal election officials that alleges Stephen Bannon—recently named one of Donald Trump’s top White House advisers—may have gotten paid illegally during Trump’s campaign by pro-Trump billionaires.

And now, a new set of Federal Election Commission filings that haven’t yet been reported on may give the group’s case some additional heft.

At issue are payments of nearly $200,000 that a super PAC called Make America Number 1 made to a company tied to Bannon. On Aug. 17, Bannon left his post as chairman of Breitbart News and became the Trump campaign’s CEO. Available FEC filings show the campaign didn’t pay Bannon a salary. Larry Noble, General Counsel for the Campaign Legal Center, said he believes the super PAC covertly paid Bannon for his campaign work through his moviemaking company. Neither the super PAC nor Bannon provided a response to Noble’s comment.

In an Oct. 6 complaint to the Federal Election Commission, the Campaign Legal Center argued that Robert and Rebekah Mercer—a father-daughter duo who give generously to conservative causes and candidates—broke federal campaign laws by paying Bannon for his work so the campaign wouldn’t have to shoulder the cost. Robert Mercer is a reclusive billionaire hedge-fund manager, and his daughter oversees much of his political giving. She’s also on Trump’s transition team.

The Campaign Legal Center says the new FEC filings undergird their case against the Mercers. Those filings cover the final weeks before Election Day, up until Nov. 5, and they show that a super PAC funded largely by the Mercers—Make America Number 1—paid Bannon’s moviemaking company, Glittering Steel, $187,500 during that window of time. The super PAC cut Glittering Steel five checks from Oct. 1 to Nov. 5: one for $40,500, one for $50,000, one for $37,500, one for $34,500, and one for $25,000.

There’s scant public information available about Glittering Steel, and the company doesn’t have a website. Sources familiar with the company told The Daily Beast this month that it’s essentially a front for Bannon, and that Rebekah Mercer is also involved with it. The company is listed as a producer of the film Clinton Cash, based on a book of the same title that ripped into Hillary Clinton and her family’s foundation for alleged influence-peddling. That narrative played a major role in Clinton’s ultimate loss to Trump.

It isn’t clear how many people Glittering Steel employs and what—if any—firewall existed to separate Bannon’s work for the Trump campaign from his company’s work for the Mercers’ pro-Trump super PAC.

Noble says his group will likely highlight these latest FEC filings to the agency as part of its case against Bannon and the Mercers.

“This is further evidence in support of the allegation in our FEC complaint that the Make America Number 1 super PAC was making illegal in-kind contributions to the Trump Campaign by paying compensation to Steve Bannon through Glittering Steel while he was working for the campaign,” he told The Daily Beast.

The FEC is already scrutinizing the Mercers’ super PAC. In a letter dated Nov. 9, FEC analyst Laura Sinram noted the PAC’s treasurer hadn’t signed one of its reports on an independent expenditure. The treasurer is required to sign all those documents to promise that the super PAC didn’t illegally coordinate with the campaign. Kristina Hernandez, a spokesperson for Make America Number 1, told The Daily Beast last week that the PAC’s lawyers will resolve the FEC’s queries.

Bannon, who is at the center of this questionable dealing, is poised to become one of the most powerful figures in the Trump White House. Trump’s transition team announced Sunday that he will be Trump’s chief strategist and senior counselor. Their statement on the hire said he will work as an equal partner with the president-elect’s White House chief of staff, Reince Priebus. Operatives close to Trump say they expect Bannon to have much more clout than Priebus.

Over the years, the Mercers have helped finance Bannon’s anti-establishment efforts, especially Breitbart News.

Trump’s closing argument against Hillary Clinton was that his candidacy would “drain the swamp” in Washington D.C. Given the alleged ties between his top donor and advisor, Trump’s swamp-draining might need to start at home.