Sen. Lamar Alexander (R-TN) announced Monday he will not seek re-election in 2020.

My statement on the 2020 Senate election. https://t.co/RUv8Biqdgd pic.twitter.com/W9U6OvmH75 — Sen. Lamar Alexander (@SenAlexander) December 17, 2018

“I will not be a candidate for re-election to the United States Senate in 2020,” Alexander said in a statement. “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. I am deeply grateful, but now it is time for someone else to have that privilege. 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.”

The longtime lawmaker said he will serve out the remainder of his term. The 78-year-old Alexander, who was elected to the U.S. Senate in 2003 and currently serves as chairman of the Senate Committee on Health, Education, Labor and Pensions, is the first senator up for re-election in 2020 to announce their retirement.

Akin to Sen. Bob Corker’s (R-TN) retirement, political observers say Alexander’s announcement, will send “shockwaves” throughout Tennessee’s political scene, according to Tennessean. Possible replacements for the U.S. Senate seat include Rep.-elect Mark Green (R-TN), Gov. Bill Haslam (R), Rep. Diane Black (R-TN) and Knoxville businessman Randy Boyd.

Alexander served as the Governor of Tennessee between 1979 and 1987 and the Secretary of Education under President George H. W. Bush.