 After serving as vice president of the Chicago-North Western Transportation Co. from 1974 to 1976, he was elected to Congress in 1976 and was re-elected three times.He resigned in 1984 to run for the United States Senate but lost to incumbent Senator Charles Percy in the primary.In 1985, Cocoran announced his intention to run for the United States Senate against Democratic incumbent Alan J. Dixon in the 1986 Senate election.