S.C. Code § 7-11-50
If a party nominee who was nominated by a method other than party primary election dies, becomes disqualified after his nomination, or resigns his candidacy for a legitimate nonpolitical reason as defined in this section and sufficient time does not remain to hold a convention to fill the vacancy or to nominate a nominee to enter a special election, the respective state or county party executive committee may nominate a nominee for the office, who must be duly certified by the respective county or state chairman.
"Legitimate nonpolitical reason" as used in this section is limited to:
A candidate who withdraws based upon a legitimate nonpolitical reason which is not covered by the inclusions in (a), (b) or (c) has the strict burden of proof for his reason. A candidate who wishes to withdraw for a legitimate nonpolitical reason shall submit his reason by sworn affidavit.
This affidavit must be filed with the state party chairman of the nominee's party and also with the board of voter registration and elections of the county if the office concerned is countywide or less and with the State Election Commission if the office is statewide, multi-county, or for a member of the General Assembly. A substitution of candidates is not authorized, except for death or disqualification, unless the election commission to which the affidavit is submitted approves the affidavit as constituting a legitimate nonpolitical reason for the candidate's resignation within ten days of the date the affidavit is submitted to the commission. However, where this party nominee is unopposed, each political party registered with the State Election Commission has the privilege of nominating a candidate for the office involved. If the nomination is certified two weeks or more before the date of the general election, that office is to be filled at the general election. If the nomination is certified less than two weeks before the date of the general election, that office must not be filled at the general election but must be filled in a special election to be held on the second Tuesday in the month following the election, provided that the date of the special election to be conducted after the general election may be combined with other necessary elections scheduled to occur within a twenty-eight day period in the manner authorized by Section 7-13-190(D).
S.C. Code § 7-11-50