Sen. Kyrsten Sinema’s (I-AZ) announcement that she would not seek a second term is sparking fresh concerns about the future of the filibuster, a rule that has forced bipartisanship in the Senate.

Along with Sinema, Sen. Joe Manchin (D-WV) will also be retiring at the end of this term. The pair served as a roadblock to prevent the erosion of the 60-vote threshold to end debate that gives the minority party the power to block legislation. The two senators prevented the weakening of the filibuster in 2022 when Democrats wanted to pass sweeping voting rights legislation.