Sen. Richard Shelby (R-Ala.) announced Monday that he will not seek re-election in 2022.

Why it matters: The 86-year-old lawmaker is the top Republican on the powerful Senate Appropriations Committee. He was first elected to the Senate in 1986 as a Democrat, before changing parties in 1994.

• Throughout his six terms, Shelby chaired a trio of highly influential committees — banking, intelligence and rules — before heading appropriations.

The big picture: Shelby is the fourth Senate Republican to announce his retirement in 2022, following Rob Portman (Ohio), Richard Burr (N.C.) and Pat Toomey (Pa.).

• His retirement could set off an intra-party scramble for a replacement, as Republicans navigate which direction to take the party following the presidency of Donald Trump.
• Democrats are thought to have little chance in deep-red Alabama, where Tommy Tuberville knocked off incumbent Democratic Sen. Doug Jones by more than 20 points in November.

What he's saying: “Today I announce that I will not seek a seventh term in the United States Senate in 2022. For everything, there is a season,” Shelby wrote in a statement.

• “I am grateful to the people of Alabama who have put their trust in me for more than forty years. I have been fortunate to serve in the U.S. Senate longer than any other Alabamian."
• “Although I plan to retire, I am not leaving today. I have two good years remaining to continue my work in Washington. I have the vision and the energy to give it my all.”

Editor's note: This post has been corrected to reflect that Shelby is in his sixth term in the Senate (not his seventh).