Leave it to Republicans to mess up a South Carolina House seat. This week former governor Mark Sanford, who left office in disgrace after an affair and four-day disappearance from the state, finished first in the South Carolina 1st congressional district  GOP primary and advanced to a runoff with Charleston attorney Curtis Bostic, who mobilized churches around the state but largely avoided debates and other candidate events. A South Carolina Republican and veteran of many state races predicts that 80 percent of Bostic’s voters will turn out no matter what comes out between now and the runoff, with the remainder somewhat gun-shy about a candidate who hasn’t been thoroughly vetted. If, as many expect, Sanford wins the runoff, the South Carolina insider fears Republicans “are absolutely in danger of losing the seat.”

An early warning was sounded by Penny Nance, head of the 500,000-member conservative Concerned Women for America. She e-mailed me, “First place does not mean he will necessarily win.  We see this in convention politics often. Usually the person who wins the first ballot loses.” She continued, “It’s hard to say, but I can’t imagine a tougher sell against the narrative of a Republican war on women. Really?!”

That, in large part, is because his opponent is, contrary to some characterizations, not a pushover. Stephen Colbert’s sister, Elizabeth Colbert Busch, won the Democratic nomination easily. She’s well known in the state, is a centrist Democrat and is well-connected among business leaders (she’s worked for Clemson University in business development). Moreover, as a former donor to Sanford’s gubernatorial campaign (although she says she didn’t vote for him), she is perfectly positioned to make the case that she’s a typical South Carolinian who was betrayed by his shenanigans.

So far Sanford has been coasting by on an argument that he deserves forgiveness for his “walk along the Appalachian Trail,” abandoning the state without telling anyone of his whereabouts and using taxpayer funds (which he eventually returned) for his home-wrecking affair with his Argentinian girlfriend.

He is vulnerable either in the runoff or in the general election if an opponent can make the argument that religious or personal forgiveness requires the wrongdoer to reject his past behavior (he’s marrying the girlfriend) and, more important, doesn’t require investing him with the public’s trust. Moreover, Sanford’s record as governor was thin on accomplishments and large on PR stunts (like bringing two pigs to the statehouse). To the extent voters are sick of Beltway gridlock and political grandstanding, a candidate like Colbert Busch, who appeals to serving her constituents and getting things done, may have some appeal.

All of that said, Sanford remains the front-runner in the runoff and the general election, considering the district’s heavy GOP tilt. Colbert Busch will attract money and media coverage, but she still would be the underdog. The state and national GOP, and social conservatives in particular, have every reason to fear, as the South Carolina veteran says, that they’ll be “the laughing stock of the whole country.” Indeed, Sanford makes a mockery of both family values and fiscal prudence (taking the taxpayers to finance a personal dalliance is not exactly in keeping with financial conservative values).