The current Senate is 48 DNC 3 Indie and 49 RNC. The Indie caucus with the DNC to select majority leader who calls bills to vote, just after the 2022 midterms the breakdown was actually 50 RNC 2 Indie but the VP was the tiebreaker.

Once legislation is called a vote it can pass in 2 ways: majority vote or supermajority vote. In the first case, the opposing party can "filibuster" in which they debate for as long as possible to delay the vote until congress gives up and returns home to their families or runs out of funding, the longest recorded filibuster was 60 days. In the second case, a supermajority can directly bypass the filibuster and pass the law immediately.

The last Supermajority on record was for about a month in the 111th US Congress in 2009-2010 because technically the DNC and Indie together had 60 votes, but also technically the DNC never had more than 58 since the 95th Congress in 1977-1978.