The 1978 United States Senate election in Iowa took place on November 7, 1978. Incumbent Democratic Senator Dick Clark ran for re-election to a second term but was defeated by Republican former Lieutenant Governor Roger Jepsen. This was the last time until 2014 that a Republican would win Iowa's Class II Senate seat.
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Text from the Wikipedia article “1978 United States Senate election in Iowa”, available under CC BY-SA 4.0.