1. Arizona: Incumbent Mark Kelly (D) is facing former Senator Martha McSally (R) in a rematch of their 2020 special election battle, which Kelly won.
2. Georgia: Incumbent Raphael Warnock (D) and appointed Senator Jon Ossoff (D) are up for reelection in the Peach State, where Republicans are expected to make a formidable effort to take back control of the Senate.
3. North Carolina: Incumbent Richard Burr (R) is retiring in 2022, leaving an open seat in a state long considered a Republican stronghold.
4. Pennsylvania: Incumbent Bob Casey Jr. (D) is up for reelection in a state where Democrats have become increasingly competitive in recent years.
5. Wisconsin: Incumbent Ron Johnson (R) is up for reelection in 2022, an election many experts believe could lead to a major shift in the balance of power in the Senate.