The chairman of the Senate Foreign Relations Committee, Sen. Bob Corker, R-Tenn., announced Tuesday that he will leave the Senate when his term expires next year, and will not seek re-election.

“After much thought, consideration and family discussion over the past year, Elizabeth and I have decided that I will leave the United States Senate when my term expires at the end of 2018,” Corker said in a statement Tuesday.

During his 2006 Senate election, Corker said he noted that he “couldn’t imagine” serving for more than two terms—that time will expire in November 2018.

“Understandably, as we have gained influence, that decision has become more difficult,” Corker said. “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.”

Corker said that he believes the “most important public service” he has to offer “could well occur over the next 15 months” of his term.

“I want to be able to do that as thoughtfully and independently as I did the first 10 years and nine months of my Senate career,” Corker said. “Serving the people of Tennessee in this capacity has been the greatest privilege in my life.”

Corker spent the month of August traveling across his district, and said he was “reminded” that Tennesseans lived in a “unique place full of people who care deeply about the direction of our country.”

“I know that we will continue to have an impact for the remainder of our term, and I look forward to finding other ways to make a difference in the future,” Corker said, thanking his “extraordinary” staff and his family.

“Nothing I have done would have been possible without their love and support,” Corker said.

Sen. Lamar Alexander, R-Tenn., said Corker’s absence will “leave a big hole” in the Senate.

“Even when he’s been investigating smugglers’ tunnels near the Gaza strip, talking to foreign leaders, or giving advice to President Trump, Bob has never let his feet leave the ground in Tennessee,” Alexander said in a statement. “His absence will leave a big hole in the United States Senate, but I know he’s carefully weighed his decision, and I’m looking forward to seeing what he tackles next.”

As for 2018 hopefuls, Tennessee conservative activist Andy Ogles announced last week that he would run for the Senate seat, along with Fox Sports analyst Clay Travis, who has said he has been “toying with” the idea of running.