The previous Democratic governor had been defeated by a Republican reformer, Winthrop Rockefeller. Bumpers ran for election against Rockefeller in 1970 as a new type of Democrat who would bring reform to the Democratic Party. Bumpers defeated Rockefeller and ushered in a new era of youthful reform-minded governors. Bumpers served as governor from 1971 to 1975, when he was elected to the United States Senate. He served in the Senate from 1975 to 1999, and was chairman of the Committee on Small Business and Entrepreneurship. Bumpers was known for his oratorial skills.
Bumpers and his wife Betty were both known for their dedication to the cause of childhood immunization.
Bumpers was never a particularly close political ally of President Bill Clinton but gave an impassioned speech in defense of him during Clinton's impeachment trial.