Cohen: 50–60% 60–70% 70–80%
The 1978 United States Senate election in Maine was held on November 7, 1978. Incumbent Democratic U.S. Senator William Hathaway decided to run for re-election to a second term, but was defeated by William Cohen, the Republican nominee and the U.S. Representative from Maine's 2nd congressional district. No incumbent Senator has lost by such a large margin since Hathaway's 22.65-point loss.
|Democratic||William Hathaway (incumbent)||127,327||33.94%||-19.29%|
|Independent||Hayes E. Gahagan||27,824||7.42%|
|Independent||John J. Jannace||5,553||1.48%|
|Republican gain from Democratic||Swing|