Republican Sen. Lamar Alexander announced Monday he will not run for re-election in 2020, saying it’s time for “someone else” to have the privilege of representing Tennessee in the Senate.

“I will not be a candidate for re-election to the United States Senate in 2020,” the 78-year-old Alexander said in a statement.

Alexander, the chairman of the Senate Health, Education, Labor and Pensions Committee, previously served as governor of Tennessee. He also worked as secretary of the Department of Education under then-President George H.W. Bush.

“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,” he said. “I am deeply grateful, but now it is time for someone else to have that privilege.”

He added, “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.”

Alexander’s retirement comes as the state’s other Republican senator, Bob Corker, opted against running for re-election this year. Republican Marsha Blackburn defeated Democrat Phil Bredesen, the state’s former governor, in that contest.

"As one of the finest statesmen our state has ever seen, Lamar will leave behind a remarkable legacy," Corker said in a statement. "I know he will press through the next two years with great vigor, and I look forward to all he will accomplish on behalf of Tennesseans as he completes his service in Washington."

Alexander's retirement is expected to spark a competitive race for the seat.

Fox News' Chad Pergram contributed to this report.