Bernard Sanders is an American politician who has served as the junior United States Senator from Vermont since 2007 and as U.S. Representative for the state's at-large congressional district from 1991 to 2007. Sanders is the longest-serving independent in U.S. congressional history, though he has a close relationship with the Democratic Party, having caucused with House and Senate Democrats for most of his congressional career. Sanders ran unsuccessfully for the 2016 Democratic nomination for president and is running again in 2020. Before entering each race, he pledged to serve as a Democrat if elected.