Washington, D.C., is governed by a mayor and a 13-member city council. However, the United States Congress has supreme authority over the city and may overturn local laws. Residents of the District therefore have less self-governance than residents of the states. The District has a non-voting, at-large Congressional delegate, but no senators. D.C. residents could not vote in presidential elections until the ratification of the Twenty-third Amendment to the United States Constitution in 1961.