South Dakota was the only state in the 1912 United States presidential election to not have the sitting U.S president William Howard Taft on the ballot or as a write in (as he was in California) which prevented the spoiler effect from happening which gave the state to Theodore Roosevelt. With 50. 56% of the popular vote, South Dakota was also the only state in which Roosevelt won a majority of the vote and the only state outside the solid south give a majority to any candidate as well as being his strongest state nationally[1].
Results
United States presidential election in South Dakota, 1912[2]