The President Pro Tempore of the United States Senate is the second ranking highest official in the United States Senate. The Vice President of the United States Senate oversees the work of the Senate, and casts the deciding vote in the event of a tie. In the absence of the Vice President, the President Pro Tem presides over the business of the Senate.
The President Pro Tem is traditionally the most senior member of the majority party in the Senate. The President Pro Tem is third in line in the order of presidential succession, following the Vice President and the Speaker of the House of Representatives.