Following graduation from high school, he attended Phillips University in Enid, Oklahoma, earning a bachelor's degree in history in 1950.

During his tenure in the state legislature, he also earned master's and doctoral degrees in political science from the University of Missouri.

Unable to seek a third term as State Treasurer in 1980, he was an unsuccessful candidate for Governor of Missouri, losing the Democratic Party nomination to incumbent Joseph P. Teasdale.

Spainhower threw his hat into the ring for the 1976 United States Senate election in Missouri after the initial Democratic nominee Jerry Litton was killed while flying to the victory party.

On August 21, the Democratic state committee selected Warren E. Hearnes as the replacement nominee over Spainhower by a 38 to 22 vote.