Article I, Section 3: The Senate

Senators are elected every six years, and each state has two Senators. Until 1913, Senators were elected by state legislatures. This clause was amended by the Seventeenth Amendment, providing for popular election of senators. Senators must be thirty and have lived in the United States at least nine years. The vice president of the United States serves as president of the Senate, but has no vote except in the case of a tie.