Robert Alphonso Taft Sr. was an American politician, lawyer, and scion of the Republican Party's Taft family. Taft represented Ohio in the United States Senate, briefly served as Senate Majority Leader, and was a leader of the conservative coalition of Republicans and conservative Democrats who blocked expansion of the New Deal. Often referred to as "Mr. Republican", he co-sponsored the Taft–Hartley Act of 1947, which banned closed shops, created the concept of right-to-work states, and regulated other labor practices.

The positions of majority leader and minority leader are held by two United States senators and people of the party leadership of the United States Senate. They serve as a chief spokespersons for their respective political parties holding the majority and the minority in the United States Senate. They are each elected as majority leader and minority leader by the senators of their party caucuses: the Senate Democratic Caucus and the Senate Republican Conference.