Longtime columnist George Will has officially left the Republican Party, he told a group of conservatives on Friday.

Will, a conservative writer for the Washington Post, confirmed to PJ Media that he switched his Maryland party registration from GOP to unaffiliated.

At a meeting of the Federalist Society Friday in D.C., Will told the group it’s worth refusing to back Trump even if it hands the election to Democrat Hillary Clinton.

“This is not my party,” he told the group. “Make sure he loses. Grit their teeth for four years and win the White House.”

Will also cited House Speaker Paul Ryan’s (R-WI) endorsement of the bombastic New York businessman as one of his final straws before de-registering.

The columnist has criticized Trump in the pages of the Post, and Trump last month fired back, calling him a “major loser.”