5:43 PM PT: The race was called several minutes ago for Mark Sanford, who currently holds a 54-45 lead with 74% reporting. Ultimately, SC-01 demographics simply reasserted themselves: The district voted 58-40 for Mitt Romney, giving Sanford a pretty healthy cushion. He underperformed Romney by almost half, around 9 net points, which is weak, but more than good enough to prevail here.
6:11 PM PT: And 54-45 it'll be, with 99% reporting. Green Party candidate Eugene Platt took a rounds-down-to-zero percent with under 700 votes. ECB got about 4,000 votes on the Working Families Party line, versus 51,000 on the Democratic line. (South Carolina is one of eight states that allows fusion voting.)