He started his political career as a precinct worker for the Democrats. In 1964, he was a delegate to the Democratic National Convention for Nebraska and served as a delegate for that state in every convention between 1972 and 2004. He served as a member of the Nebraska Democratic State Central Committee between 1964 and 1968 and was a member of the Democratic National Committee from 1968 to 1970. Exon was Chair of the Nebraska Democratic Party in 1970 when he decided to run for Governor.