Tom Steyer has announced he was adding $10 million to his effort to see President Donald Trump impeached, funding a pair of new television spots calling for the President’s removal from office.

Mr. Steyer had already poured $10 million into the effort, bankrolling spots warning that the President “is a clear and present danger who is mentally unstable and armed with nuclear weapons.”

The effort seems to have caught the attention of Mr. Trump, who assailed Mr. Steyer in a tweet as “wacky” and “unhinged” — evidently after seeing one of the impeachment adverts during a break from “Fox and Friends,” a programme the President regularly watches.

In addition to paying for ads, Mr. Steyer has pushed Democrats to make clear that they back Mr. Trump’s impeachment ahead of 2018 elections in which Democrats hope to capitalise on anti-Trump sentiment.

Should they win a majority in the House of Representatives, Democrats would have a clearer path to pursuing Mr. Trump’s impeachment.

Some Congress members have already openly talked about removing Mr. Trump, with Democrat Al Green vowing to force a vote on articles of impeachment by Christmas.

Other Democrats have sought to play down the idea of impeachment.

Mr. Steyer has argued that Democrats’ constituents broadly support impeachment, and he can marshal some evidence: his petition to impeach Mr. Trump quickly surpassed one million signatures and is approaching two million.