(Kudos, by the way, to Public Policy Polling, the only firm willing to offer public numbers for a difficult-to-poll runoff. They put Sanford up 53-40, a 13-point margin; he won by 14. It's hard to do much better than that.)
Now Sanford will face Democrat Elizabeth Colbert Busch, sister of comedian Stephen Colbert. (She pronounces it "cole-bert," unlike her brother.) Despite this district's very red hue—Mitt Romney carried it 58-40 last November—Colbert Busch had a narrow 47-45 lead over Sanford in PPP's survey, and a similar 47-44 edge in an internal poll she released earlier this week. While Sanford retains a measure of popularity with some Republicans, overall, his reputation is poor, thanks in large part to his infamous hike on the Appalachian Trail as governor several years ago.
Colbert Busch's favorability ratings, on the other hand, have been strong, but that comes with a big caveat: She didn't face a competitive primary and hasn't been the subject of a single negative attack yet. That's about to change. Of course, Republicans shouldn't have to break a sweat holding a seat like this, so the fact that they're almost sure to go negative on Colbert Busch is a testament to Sanford's... special qualities, and perhaps the weakness of the GOP brand in general. I wouldn't rule out the chance of an upset, especially if Colbert Busch gets serious outside help and can make the race all about Sanford. (Indeed, her famous brother is going all-out and raising lots of money for her, and New York Sen. Kirsten Gillibrand is aiding her cause, too.)
Colbert Busch has her own vulnerabilities, though they are mostly ideological, simply because she's a Democrat running in such a red district. In one tweet, for instance, she declared she was "both pro-choice and in favor of marriage equality," stances that put her to the left of the median voter in SC-01—and tellingly, her campaign just wiped her entire Twitter account clean. But as one local Republican operative quoted by Politico notes, it may be tricky for Sanford himself to go on the offensive, seeing as he's still busy apologizing for his indiscretions and many women voters still have a serious problem with him. And the fact that his opponent is a woman doesn't make it any easier.
That likely means that outside groups—principally the NRCC—will have to do Sanford's proverbial "dirty work" for him. And if national Republicans wind up having to spend real money here, that alone is a victory for Democrats. But with the GOP saddled with a candidate as flawed as Sanford, an outright victory for Team Blue is not impossible. So, as always, keep an eye on fundraising, attack ads, outside spending, and, of course, polling, because we might just see a surprise here.