Susan Margaret Collins (born December 7, 1952) is an American politician who currently serves as the senior United States Senator from Maine. A member of the Republican Party, Collins has served in the Senate since 1997, and has served as the Chairman of the Senate Special Committee on Aging since 2015 and previously chaired the Senate Committee on Homeland Security from 2003 to 2007. She is considered to be one of the most moderate Republicans in office.