Sen. Bob Corker announced Tuesday he will not seek re-election in 2018. “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,” the Republican senator said in a statement. “When I ran for the Senate in 2006, I told people that I couldn’t imagine serving for more than two terms. 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.” Corker, a two-term senator who currently chairs the Senate Foreign Relations Committee, has been a vocal critic of President Trump and potentially faced an electoral threat from the right. Last month, Corker told reporters that the president has yet to show the “stability” or “competence” necessary to be a successful leader. “He also recently has not demonstrated that he understands the character of this nation,” the senator added.