Billionaire investor and conservative donor Robert Mercer is stepping down as the co-CEO of Renaissance Technologies effective Jan 1.

According to Bloomberg News, Mercer, 71, sent a letter to investors on Thursday saying that he would step down from atop the hedge fund at the beginning of 2018 and would leave its board as well.

He said he would remain on the company's technical staff focusing on research.

The decision comes as another one of Mercer's companies, the data mining and analysis firm Cambridge Analytica, is facing scrutiny for its role in the 2016 presidential election.

In October, The Daily Beast reported that Alexander Nix, the CEO of the firm, which was paid millions by Trump's campaign during the election, told a third party that he had reached out to WikiLeaks founder Julian Assange about Hillary Clinton Hillary Diane Rodham ClintonWhat Senate Republicans have said about election-year Supreme Court vacancies Bipartisan praise pours in after Ginsburg's death Trump carries on with rally, unaware of Ginsburg's death MORE's emails.

The report has fueled further questions about Russian election interference and led Trump aides to distance the campaign from the firm.

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At the same time as his decision to step down from Renaissance, Bloomberg reported that Mercer would sell his stake in Breitbart News to his daughter Rebekah Mercer, another prominent backer of conservative causes.

Mercer did not offer an explanation for selling the shares but said that he was choosing to do so "for personal reasons," according to a letter obtained by Bloomberg.

In the letter, Mercer sought to distance himself from Stephen Bannon, former White House chief strategist and current executive editor at Breitbart News, saying that, while he occasionally discusses politics with Bannon, they do not share all of the same views.

"I have great respect for Mr. Bannon, and from time to time I do discuss politics with him. However, I make my own decisions with respect to whom I support politically. Those decisions do not always align with Mr. Bannon's."

Mercer also took aim at Milo Yiannopoulos, the controversial former Breitbart editor and provocateur. The hedge fund CEO said that he initially supported Yiannopoulos in hopes to challenging political correctness, but that his statements only served to deep social and political divides.

"In my opinion, actions of and statements by Mr. Yiannopoulos have caused pain and divisiveness undermining the open and productive discourse that I had hoped to facilitate. I was mistaken to have supported him, and for several weeks have been in the process of severing all ties with him."

Mercer and Peter Brown took over as the hedge fund's co-CEOs in 2010 after the firm's founder, James Simons, a prominent Democratic donor, retired. Simons remains the chairman of Renaissance's board.

Larry Solov, Breitbart's president and CEO, revealed earlier this year that the Mercers, who spent millions to support President Trump's 2016 campaign, were part owners of the conservative news site.

Both Robert and Rebekah Mercer have been backers of Bannon, the former White House chief strategist who returned to the top post at Breitbart in August after leaving the Trump administration.

Bannon, a self-described economic nationalist, was widely seen as a driving force behind Trump's populist brand of conservatism.