Max Sieben Baucus is an American politician and diplomat who served as a United States Senator from Montana from 1978 to 2014. A member of the Democratic Party, he was Montana's longest-serving U.S. Senator and became the third longest-serving senator in history at the time of his retirement. During his tenure, he chaired the influential Senate Committee on Finance, playing a key role in debates on health care reform, including the Affordable Care Act. After leaving the Senate, Baucus served as the United States Ambassador to China from 2014 to 2017.