Clarence William Nelson II is an American attorney and politician who served as a United States Senator from Florida from 2001 to 2019. A member of the Democratic Party, he previously served in the Florida House of Representatives from 1972 to 1978 and in the United States House of Representatives from 1979 to 1991. In January 1986, he became the second sitting member of Congress to fly in space when he served as a payload specialist on the Space Shuttle Columbia. Before entering politics he served in the U.S. Army Reserve during the Vietnam War.