Arizona Republican Jeff Flake, a U.S. Senator who has earned Trump’s ire after repeated critiques of the President’s words and actions, announced today that he will not run for re-election.

Condemning the nastiness of Republican politics in the era of President Trump, Sen. Jeff Flake on Tuesday announced he will serve out the remainder of his term but will not seek re-election in 2018.

The bombshell, which Flake, R-Ariz., intended to detail Tuesday afternoon on the Senate floor, will further roil Republican hopes of keeping the party’s 52-seat Senate majority in the midterm elections of Trump’s first term, when the president’s party historically loses seats in Congress.

Flake was set to face multiple challenges from both the left and the right. Kelli Ward, a serial Senate candidate and outspoken Trump supporter in Arizona, is one of those challengers.

Arizona’s junior Senator has been involved in multiple spats with Trump since the latter took office, with many Trump supporters, including Steve Bannon, looking to recruit challengers to Flake and other Trump critics within the Senate and the House.

However, Flake’s re-election was anything but sure to begin with. His chances of winning the Republican primary were getting slimmer by the day, and it seemed as though his best chances lay in an extremely divided field to weaken his opposition.

Flake’s departure from the Senate leaves a question mark for Republicans, who are afraid of either losing the seat or handing it over to a more Trump-like replacement.