Vice President - the person who takes over the Presidency in case of illness or death of the President. The Vice President also acts as president of the Senate, over which he presides. He or she may not vote in the Senate, except to break a tie. Presidential candidates often choose running mates to attract support from voters otherwise disinclined to vote for them. For most of American history, the role of the Vice President was very limited. Under the presidencies of Carter, Reagan and Clifton, however, the Vice President has been given more responsibilities.