Max Sieben Baucus (born December 11, 1941) is an American politician. He was the United States Ambassador to China from 2014 through 2017. He served as a United States Senator from Montana from December 15, 1978 until February 6, 2014. On that date, he was made Ambassador. He is a member of the Democratic Party. He was Montana's longest-serving U.S. senator.