Sen. Bob Corker (R-Tennessee) announced Tuesday afternoon he will not seek re-election in 2018. The news broke just hours before the results were announced in the Alabama primary race for Jeff Sessions’ Senate seat between Luther Strange, who Donald Trump endorsed, and his opponent Roy Moore.

“When I ran for the Senate in 2006, I told people that I couldn’t imagine serving for more than two terms,” Corker said in a statement, according to Politico. “Understandably, as we have gained influence, that decision has become more difficult. But I have always been drawn to the citizen legislator model, and while I realize it is not for everyone, I believe with the kind of service I provide, it is the right one for me.”

Deep-pocketed GOP donor Lee Beaman pledged last week to raise $4 million for Corker’s opponent, Andy Ogles. Corker’s decision not to run again could dramatically alter the political landscape for Republicans during 2018’s midterm elections. His announcement also falls on the heels of congressional Republicans’ repeated failures to repeal and replace Obamacare and accomplish much of any agenda despite full control of both legislative branches, which has frustrated much of the base.