 In 1984, Dunn made an unsuccessful run for the U.S. Senate seat held by Democrat Carl Levin, losing in the Republican primary to Jack R. Lousma.In 1986, he ran for the 6th district seat, and again lost in the general election to Bob Carr.In 1988, he won the Republican nomination to the U.S. Senate, having defeated former U.S. Representative Robert J. Huber, who had left office in 1975.