S.C. Code § 2-20-25
A person serving in an office elected by the General Assembly who is not seeking reelection must give written notice to the joint committee to review candidates for that office of his decision not to seek reelection. The notice must be given not less than thirty days before the last date for filing for that office. If the notice is given less than thirty days before the last date for filing for that office or if the notice is withdrawn and the person seeks reelection, the joint committee may reopen or extend, as appropriate, the time period for filing for the office. For purposes of this subsection, "person serving in an office elected by the General Assembly" includes a person serving in office as an appointee to an unexpired term.
S.C. Code § 2-20-25