Kyrsten Sinema (D-AZ) and Joe Manchin (D-WV) are the two senators currently standing in the way of the Democratic Party abolishing or carving out exceptions to the Senate filibuster. This is currently the only way for President Joe Biden's party to pass a law codifying the right to abortions at the federal level after Supreme Court precedent Roe v. Wade was overturned. The same senators came out in 2021 against filibusters abolition or weakening to end the problem of the U.S. debt ceiling in the medium term.
The Democrats currently have a 51:50 majority in the upper chamber of U.S. Congress (including Vice President Kamala Harris’ tie-breaking vote), which is short of the 60 votes needed to end a filibuster. Through the filibuster, the minority party in the Senate can hold up proceedings by not letting bills come up to a vote if the majority party lacks a majority of 60 votes or more. To abolish or carve out an exception to the filibuster, Democrats would presumably only need a simple majority, but due to intra-party dissenters, they also do not have that one.
Numbers from the U.S. Senate suggest that filibusters – and the motions needed to end them – have indeed been more frequently holding up business on Capitol Hill as the often-invoked partisan gridlock becomes ever more entrenched. The 117th Congress, still in session until the end of this year, is close to setting a new record for Senate cloture motions filed to end filibusters. The current one is held by the previous Congress at 328. For the current one, the number stood at 293 with several months still to go in the term.