South Carolina's famously rough politics are testing a relative newcomer who is hoping tea-party support will help her succeed embattled Gov. Mark Sanford. State Rep. Nikki Haley has emerged from the back of the pack over the past month to take the lead in the polls ahead of Tuesday's Republican gubernatorial primary. Her message of limited government has resonated with voters, as well as the endorsements from former Alaska Gov. Sarah Palin and one of the state's most popular political figures—the governor's ex-wife, Jenny Sanford. But Mrs. Haley is navigating allegations of marital infidelity made by two men, one an...