S.C. Code Ann. § 7-15-360

The board of registration of each county must be furnished by the commissioners of election of the county or the county committee for each political party holding a primary, a sufficient number of ballots and envelopes not to exceed fifteen percent of the number of registered voters in that county to enable the board of registration to deliver these materials to qualified electors who desire to vote by absentee ballot. If an absentee ballot is not available at the time the voter requests it, the board of registration must provide a blank ballot to allow the voter to write in his: (1) selections of candidates; (2) selection of party, if he wishes to vote a straight party ticket; and (3) support or opposition of any ballot measure.