The former director of the Office of Government Ethics on Monday called for members of Congress to take action if special counsel Robert Mueller is fired.

"Every Member of Congress who cares about the republic should pledge now to take decisive action against the White House if Mueller is fired," Walter Shaub tweeted Monday.

Every Member of Congress who cares about the republic should pledge now to take decisive action against the White House if Mueller is fired. — Walter Shaub (@waltshaub) October 30, 2017

His comments came after President Trump's former campaign chairman, Paul Manafort, was told to turn himself in Monday in what appears to be the first arrest related to Mueller's investigation into Russian election interference.

ADVERTISEMENT

The charges against Manafort and business partner Rick Gates are not yet known. The indictments remain under seal by a federal judge.

Manafort’s arrest marks a significant milestone in Mueller’s investigation into alleged ties between Trump campaign associates and Russian officials.

President Trump has in the past decried the Russia probe as a "witch hunt" and he and his aides have denied collusion.

On Sunday, Trump said it's no coincidence that news surrounding Mueller's investigation was surfacing at the same time Republicans are pushing tax reform.

"All of this 'Russia' talk right when the Republicans are making their big push for historic Tax Cuts & Reform," Trump wrote on Twitter. "Is this coincidental? NOT!"