Robert Marion "Young Bob" La Follette Jr. (February 6, 1895 – February 24, 1953) was an American politician serving as a U.S. Senator from Wisconsin from 1925 to 1947. A member of the La Follette family, he was a son of U.S. Representative, U.S. Senator and Wisconsin Governor Robert M. La Follette Sr., and father of Wisconsin Attorney General Bronson La Follette. As co-founder of the Progressive Party and ally of the Farmer-Labor Party in adjacent Minnesota, La Follette kept the Progressive Party alive in the US Senate until his defeat by Joseph McCarthy in 1946.