John Thune is an American politician serving as the senior United States senator from South Dakota, a seat he has held since 2005. A member of the Republican Party, he has been the Senate majority leader and Senate Republican leader since January 2025. Thune is in his fourth Senate term and is the dean of South Dakota's congressional delegation. From 1997 to 2003, he served three terms as the U.S. representative for South Dakota's at-large congressional district. Thune has worked in politics and civic organizations since completing his MBA degree. He first ran for the U.S. Senate in 2002, losing to incumbent Senator Tim Johnson. In 2004, he defeated Senate Democratic Leader Tom Daschle. In the Senate, Thune served as the Republican chief deputy whip from 2007 to 2009 and chaired the Senate Republican Policy Committee from 2009 to 2012. He served as the Senate Republican Conference chair, the third-ranking position in the Senate, from 2012 to 2019. The Senate Republican Conference selected Thune as the majority whip for the 116th Congress; he succeeded Senator John Cornyn of Texas, who was term-limited in the position. In 2020, he was chosen as minority whip for the 117th Congress. In 2024, he was elected Senate Republican leader, succeeding Mitch McConnell. Thune is the first Senate party leader to have originally taken office as a senator in the 21st century.