 In 1990, Peterson ran as a Democrat for a seat in the United States House of Representatives in Florida's 2nd congressional district.He defeated James W. Grant, a politician who grew unpopular after switching from the Democratic Party to the Republican Party in the middle of his second term.He declined to run for a fourth term (he was succeeded by Allen Boyd) and in 1997 was asked by President Bill Clinton to become the United States's first post-war ambassador to Vietnam.