1986 United States Senate election in South Dakota

The 1986 United States Senate election in South Dakota was held on November 4, 1986. Incumbent Republican U.S. Senator James Abdnor ran for re-election to a second term, but was defeated by Democrat and future Senate Majority Leader Tom Daschle. This election was the only United States Senate election in South Dakota that Daschle would win by a narrow margin.

Candidates

 * James Abdnor, incumbent U.S. Senator
 * Bill Janklow, Governor of South Dakota

Results
[[File:1986 US Senate election in South Dakota Republican Primary.svg|thumb|200px|Republican Primary results by county: {{legend|#ed8783|Abdnor}}

{{legend|#ed8783|50–60%}}

{{legend|#e55651|60–70%}}

{{legend|#d02923|70–80%}}

{{legend|#b00600|80–90%}} {{legend|#c88fe4|Janklow}}

{{legend|#c88fe4|50–60%}}

{{legend|#b368d9|60–70%}}

{{legend|#9d40cc|70–80%}} ]] Although Abdnor won the primary by a fairly comfortable margin, it hurt him badly. Daschle was uncontested for the Democratic nomination and therefore was able to focus on the general election early, while Abdnor had to fight a challenge from a popular incumbent governor. Many political analysts say this was one of the factors in Abdnor's general election loss.

Candidates

 * James Abdnor (R), incumbent U.S. Senator
 * Tom Daschle (D), U.S. Representative