Complex sentence: In 1980 he defeated incumbent Donald W. Stewart in the Democratic Senate primary, but narrowly lost the general election to Republican Jeremiah Denton, who was aided by the Ronald Reagan landslide, which helped Republican candidates across the country.
Split into simpler sentences: In 1980 he defeated incumbent Donald W. Stewart in the Democratic Senate primary. Folsom narrowly lost the general election to Republican Jeremiah Denton, who was aided by the Ronald Reagan landslide, which helped Republican candidates across the country.