SDCL § 12-24A-8: Replacement presidential or vice presidential candidate.

If, between the date of the general election and the date designated by Congress for the election of the president and vice president of the United States, the candidate for the president or vice president whose slate of electors received the highest number of votes in the state's general election withdraws, dies, or, because of a permanent disability, becomes unable to discharge the powers and duties of the office to which the candidate is elected, each presidential elector from this state must vote for the replacement candidate nominated according to the bylaws of the party to which the previous candidate belonged.