Richard Painter, the former chief ethics lawyer for President George W. Bush, announced his bid Monday for the U.S. Senate seat once held by Al Franken.

An ardent critic of President Trump and a lifelong Republican, Painter has decided to run as a Democrat, meaning he will have to defeat sitting Sen. Tina Smith, who was appointed to the seat after Franken resigned in January over sexual harassment allegations.

“We are not going to have people representing this state in the House or Senate who are unwilling to stand up to President Trump,” Painter said during his campaign announcement at the Minnesota State Capitol in St. Paul.

Painter, a regular commentator on cable news, is a boisterous Trump critic on both television and social media, and in his campaign announcement offered blunt criticism for the party he once called himself a member of.

Richard Painter speaks during the 2018 Unrig the System Summit at the McAlister Auditorium at Tulane University on Feb. 3, 2018 in New Orleans.

“The problem in the Republican Party is that they have made it very clear that nobody is welcome to be a candidate for national office that does not support Donald Trump,” Painter said, “I’m out of the Republican Party, I’m fed up.”

Painter, 56, said that Trump “has demonstrated that he is not fit for office,” and predicted that Democrats will take back both houses of Congress in November and convene hearings in the House and Senate on the president’s alleged misconduct.

“We are well past the point where the House and the Senate convened hearings on the Watergate scandal,” Painter told reporters.

Our “very stable genius” has no interest in anything practical such as family planning. He’d rather spend the money on military parades … and his EPA Administrator’s $43,000 phone booth.https://t.co/vsFMbAH6J0 via @modrnhealthcr

— Richard W. Painter (@RWPUSA) April 27, 2018

Our president is Tweeting under the influence of something or…