Tom Steyer, Democratic mega-donor and environmentalist, has demanded Democratic lawmakers and candidates pledge to to push for the impeachment of President Donald Trump if they take control of Congress next year.

Steyer, a California investor and multi-billionaire who donated more than $91 million to Democratic campaigns during the 2016 cycle, issued a letter to Democrats on Wednesday demanding a pledge to push for Trump’s impeachment, the New York Times reported.

In his message, Mr. Steyer described Mr. Trump as a “clear and present danger to the republic” and called on Democrats to pledge that they would seek to remove him from office if they take control of Congress next year.

Mr. Steyer — who is considering a run for Senate, perhaps against Senator Dianne Feinstein, a fellow Democrat — cited a range of acts by Mr. Trump to justify impeachment, including the president’s “relationship with Vladimir Putin and Russia,” allegations that Mr. Trump has used the presidency to “promote his own business interests” and his “seeming determination to go to war.”