What are Mark Sanford's chances to reclaim his House seat?

Former Gov. Mark Sanford, R-S.C., has drawn a little closer to political redemption. Just a few years after the scandal that marred the end of his gubernatorial term, Republican voters in South Carolina's 1st Congressional District have given him the nomination for the seat vacated by now-Sen. Tim Scott, R-S.C.

Sanford will now head for a May 7 showdown with Democratic nominee Elizabeth Colbert Busch in a contest with plenty of character. Sanford will and should be favored, but it's not a certainty.

It's a heavily Republican district, running along a number of wealthier areas along the coast and around Hilton Head. President Obama won just 40 percent in the district last year (even below his statewide average) so the partisan profile has to make Sanford the favorite to return to Congress. He once represented the area before becoming governor.

Still, his win in the runoff against a lesser-known and far less-funded opponent in Curtis Bostic was solid at 57 percent, but not a majority that one would term a landslide. That at least adds to the interest level heading into next month's special election, opening the question of whether Republicans will fully rally behind Sanford.

Given the partisan profile in the 1st district, the guessing here is that Colbert Busch won't want this race to be nationalized, the way some special elections are, or to be about partisan politics generally; she'll want it to be at least partly a referendum on Sanford, in hopes of pulling off a few moderate Republicans, or that many of those who would otherwise back a GOP candidate might just stay home. Sanford, for his part, has looked to mitigate this by addressing his issues head on, asking for forgiveness and appearing with his new fiancé at his victory speech last night, clearly looking to move past it and make this a race about conservative issues.

By the numbers, Sanford's fate now will rest on how well he can expand beyond his core support within the Republican primary base; the raw numbers of votes he's gotten so far in the nominating contests probably won't cut it in May, and he won't expect them to.

The primary rounds so far give us a baseline of the most committed. There was just 10 percent turnout overall Tuesday night. Sanford had gotten 19,000 votes in the initial primary - tops in the multi-candidate field, but not a majority. He then got 26,000 votes in the runoff straight-up against Curtis Bostic Tuesday night, another conservative candidate who went straight after Sanford in the runoff campaign, questioning whether the former governor could really compete in a general election given his history - but to no avail. So Sanford picked up a few more backers along the way, but his work now starts with the 20,000 votes that just went to Bostic: these are reliable voters, having turned out in this runoff, so they should be expected to normally come out in the Special.

In losing to Sanford, Bostic had sought heavy support from evangelical groups - who might have been turned off by Sanford's past behavior - and also pressed a socially conservative message. Those social conservatives might be a real wild card now. The district overall does have a mix of more fiscally- than socially-oriented conservatives among its retirees and upper-income voters. (As an illustration, the region was where Mitt Romney did his relative best in the presidential primary against Gingrich and Santorum.) The question is whether these voters will come out again for Sanford over a Democrat; whether - perhaps less likely - any might be swung to Colbert Busch; or whether they'd just as soon stay home than vote for the former governor.

In another possibly interesting sign about Republican enthusiasm, in the most recent prior primary runoff in 2010 we saw about 69,000 votes cast, compared to about 46,000 this time, though that year was one of high GOP motivation overall. Still, a competitive contest in May might provide motivation for conservatives, if the district's Republicans worry they'll lose the seat and would rather send the conservative Sanford - despite his past - than put another Democrat into the House.

By comparison, for her part, Colbert Busch starts at just around the same place. She got 15,000 votes in her primary, though it wasn't a competitive race. Of course she's had a head start on ramping up her campaign, though now that the GOP runoff is over, the dynamics will change and she'll start to draw fire.

Colbert Busch is the sister of the famous comedian Stephen Colbert, who has helped with her fundraising, and Democrats will hope for a pickup here if they can muster enough anti-Sanford sentiment. In a regular November election when the large number of voters would make that partisan edge insurmountable, that might be fantasy, but in the special election next month, turnout and organization hold sway, they'll take a run at it.

The more the special resembles a full general election, the better it probably is for Sanford. In 2012 the district gave 179,000 votes to the GOP and 98,000 to the Democrat. Larger turnout means the lopsided proportions are more likely to materialize in Sanford's favor.

The last off-year, fall general election in 2010 saw 233,000 votes cast, which would certainly be high for a special election, but more realistic expectations might top out around 150,000. The district overall is about one in five African-American, whose reliably Democratic turnout would be needed for Busch to have a chance. The Democrat in the last midterm-year general got 67,000 votes, which could be a ceiling for Colbert Busch to aim for.

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    Anthony Salvanto is CBS News elections director