Office of the President of the Senate

The Vice President of the United States is, ex officio, President of the United States Senate, with the power to cast tie-breaking votes. However, while the Vice President has the right to act as presiding officer over the Senate, the rules of the Senate give that office very little power (in contrast to the powerful office of Speaker of the House), and in practice it is often exercised by one of the most junior Senators in attendance.

While vice presidents used to regularly preside over the Senate, modern vice presidents have done so only rarely—vice presidents usually only preside to swear in new senators, during joint sessions, to announce the result of a vote on a significant bill or confirmation, and when casting a tie-breaking vote. The Senate chooses a president pro tempore to preside in the vice president's absence. Modern presidents pro tempore, too, rarely preside over the Senate. In practice, the junior senators of the majority party typically preside in order to learn Senate procedure.

The current Vice President of the United States and President of the United States Senate is Joe Biden.

Only once in U.S. history has the Vice President been elected to represent a different political party from that of the President. In 1796, Democratic-Republican Thomas Jefferson was elected vice president and Federalist John Adams President; a situation that in part prompted the later adoption of the Twelfth Amendment to prevent such a situation from reoccurring. (Though there remain some fringe Electoral College scenarios in which it could happen again.) In addition, Abraham Lincoln and Andrew Johnson were elected together on the National Union ticket in the 1864 presidential election, although Lincoln came from the Republican Party and Johnson was a War Democrat.

The vice president holds a tie-breaking (or "casting") vote in the Senate. Vice presidents have cast 242 tie-breaking votes. The vice president with the most tie breaking votes is John Adams with 29.

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