What to watch: Gov. Henry McMaster, who took the job last year after Nikki Haley joined the Trump administration, is facing a competitive Republican primary as he seeks his first full term. His opponents include his own lieutenant governor, Kevin Bryant, as well as Catherine Templeton, a lawyer whose website calls her a “conservative buzzsaw.” And while polls show Mr. McMaster leading the pack, it is not clear that he will break the 50 percent threshold needed to avoid a runoff later this month.
A competitive primary is also expected in South Carolina’s Fourth District, which is being vacated by Representative Trey Gowdy, perhaps best known for leading the House committee that investigated the Benghazi attack. The race is tremendously crowded, with 13 Republican candidates.
And in the First District, Representative Mark Sanford, a Republican once expected to win re-election with little trouble, is now in danger of losing to a primary challenger, State Representative Katie Arrington. Ms. Arrington has attacked Mr. Sanford for his criticism of President Trump.
— MAGGIE ASTOR