Republican U.S. Sen. Lamar Alexander of Tennessee says he won't seek re-election in 2020.

Alexander said in a news release that he's deeply grateful for being elected to serve more combined years as governor and senator than anyone else in Tennessee.

As a Tennessee native, Alexander is the only Tennessean ever popularly elected both Governor and U.S. Senator. His 2008 general election vote total of 1,579,477 is the largest ever received by a statewide candidate.

Lamar Alexander has served more than 24 years in public service.