The 1978 United States Senate election in Delaware was held on November 7, 1978. Incumbent Democratic senator Joe Biden won re-election to a second term, defeating Republican challenger James H. Baxter Jr. in a landslide victory. This is the first of five elections in which Biden won all counties.
The Republican Party primary was held on September 9, 1978. Venema was previously an independent before declaring himself a candidate in March 1978. Candidates Venema and Baxter were described by The Washington Post as being "two think-alike Reagan conservatives" but differed in terms of background and "personal style".