The five justices of the South Carolina supreme court are selected by the state legislature and serve 10-year terms. South Carolina and Virginia are the only two states to use some form of legislative selection when choosing supreme court justices.
The South Carolina Judicial Merit Selection Commission screens and selects candidates for judgeships then submits a list of three names to the general assembly. The assembly then votes on the candidates, either choosing one of the three recommendations or rejecting the entire slate. Of the five justices currently on the court, only one, Justice John Few, has faced a challenger for election. The other four justices ran unopposed for their respective selections.
The commission is composed of 10 members. The speaker of the House and the president of the Senate each appoint five members to the commission. Three of the five must be members of the General Assembly. The other two members are laypersons. Because of the roles of the speaker of the House and president of the Senate, the majority party in the legislature controls membership on the judicial nominating commission. If one party controls the House and another party controls the Senate, then control of commission membership is split.
South Carolina has had a Republican state government trifecta since 2003. All five of the justices serving on the supreme court were appointed during Republican control of the legislature and, thus, of the selection process.
This might indicate that all the justices on the supreme court would be Republican. However, the current chief justice, Donald Beatty, is a former Democratic state representative. He ran unopposed for the role of the chief justice and was legislatively elected in May 2016. He was the most senior member on the court prior to his selection as chief justice.
Additional Reading:
South Carolina Supreme Court
Legislative election of judges
Donald Beatty