The 1966 United States Senate election in Iowa took place on November 8, 1966. Incumbent Republican Senator Jack Miller was re-elected to a second term in office over Democrat E.B. Smith.
After this race, no incumbent would be re-elected to either of Iowa's Senate seats until Chuck Grassley was elected to his second term 20 years later.
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Text from the Wikipedia article “1966 United States Senate election in Iowa”, available under CC BY-SA 4.0.