Robert Mercer, co-chief executive of Renaissance Technologies, is resigning from his role at the giant hedge fund, according to a letter sent by Mercer to the firm’s investors,The Wall Street Journal reports.

Mercer has assumed an outsize political profile in recent years, thanks to his support for various conservative and other causes. Mercer provided crucial financial support when Donald Trump’s presidential candidacy was lagging. Mercer and his daughter Rebekah advised the campaign, suggesting the installation of two Mercer family confidantes, Steve Bannon and Kellyanne Conway, atop the campaign.