American political leader Mike Mansfield served as a Democratic Senator from Montana, and holds the record for the longest term as majority leader, having held the position for 16 years (1961-1977). He was known for his influence in foreign affairs, having strong opinions on the nation's security needs and the importance of balance-of-power relationships. Mansfield also served in the House of Representatives for 10 years, and worked on foreign diplomatic assignments under Presidents Eisenhower, Kennedy, and Johnson. President Carter appointed him ambassador to Japan, a position he retained under President Reagan.