Sen. Lamar Alexander (R-Tenn.) on Monday announced that he will not run for reelection in 2020.
"I will not be a candidate for re-election to the United States Senate in 2020. The people of Tennessee have been very generous, electing me to serve more combined years as Governor and Senator than anyone else from our state," Alexander said.
Alexander, who has been in the Senate since 2003, said he will serve out the remainder of his term, which runs through the end of 2020.
"I have gotten up every day thinking that I could help make our state and country a little better, and gone to bed most nights thinking that I have. I will continue to serve with that same spirit during the remaining two years of my term," he added.
Alexander, 78, is the first senator up in 2020 to announce that they won't seek reelection. Republicans face a challenging map during the next cycle, where they'll be defending approximately 22 seats, including in states like Colorado and Maine, which Democratic presidential nominee Hillary Clinton won in 2016.
Alexander is also the latest in a string of GOP chairmen from the establishment wing of the party to announce that they will retire during the Trump era: Senate Finance Committee Chairman Orrin Hatch (R-Utah) and Senate Foreign Relations Committee Chairman Bob Corker (R-Tenn.) are retiring at the end of the current Congress.
[ECA Note: Sen. Lamar Alexander currently serves as the chairman of the Senate Appropriations Subcommittee on Energy and Water Development. It is unclear who will take Alexander's spot as the top Republican for the subcommittee, but based on seniority, Sens. Susan Collins (R-ME) and Lindsey Graham (R-SC) are potential candidates.]