Sen. Roy Blunt (R-Mo.) will not run for re-election in 2022, he announced on Twitter Monday.

Why it matters: The 71-year-old senator is the No. 4-ranking Republican in the Senate, and the fifth GOP senator to announce he will not run for re-election in 2022 as the party faces questions about its post-Trump future.

The other GOP senators who have announced their retirement are:

• Sen. Richard Shelby (Ala., which Trump won in 2020 by +25.4%)
• Sen. Rob Portman (Ohio, Trump +8.1%)
• Sen. Richard Burr (N.C., Trump +1.3%)
• Sen. Pat Toomey (Pa., Biden +1.2%)

Background: Blunt was first elected to the Senate in 2010, after serving in the House for 14 years and as Missouri secretary of state for eight. In addition to being a member of leadership as chair of the Republican Policy Committee, Blunt is the top Republican on the powerful Senate Rules Committee.