The most common reaction to disgraced former South Carolina governor Mark Sanford's victory Tuesday in a Republican runoff for a Charleston-based House seat goes something like this: What the heck?

Former South Carolina Gov. Mark Sanford and his fiancee, Maria Belen Chapur, at his victory party on Tuesday night. AP photo.

After all, this is the same Sanford who blew up his political career in 2009 he disappeared from the Palmetto State for five days, told his gubernatorial staff he was hiking the Appalachian Trail and then acknowledged that he had been in Argentina visiting his mistress. Yes, that really happened. Sanford, who was married and had four boys, stayed in office until his term ended in early 2011. The assumption -- from The Fix and everyone else who followed the story -- was that Sanford's political career was over.

And yet, less than four years after he turned "hiking the Appalachian Trail" into the greatest euphemism for an extramarital affair ever, Sanford has emerged as the Republican nominee for the seat he once held and is given at least 50-50 odds of winning the special general election against Democratic nominee Elizabeth Colbert Busch in early May.

How did Sanford resurrect his career?  Here are five reasons.

1. People don't pay much attention to politics.  Yes, Sanford's extramarital affair was huge news in the state and nationally. But, it was also more than three years ago. Most people follow a story for as long as it is shoved in front of their faces by the media and then ignore/forget it in short order. The assumption made by the political class was that the average Joe would hold Sanford's past conduct against him. But that assumption was based on the idea that people remembered or cared enough to hold it against him. Sanford's notoriety might even have worked in his favor since everyone in the district knew/knows his name -- and in a low-attention primary fight, name ID matter a lot.

2. Sanford turned the race into a referendum on forgiveness. Rather than try to avoid his past, Sanford was open about it. In his first television ad of the race, Sanford sought to turn his past into a strength. “I’ve experienced how none of us go through life without mistakes,” Sanford said in the commercial. “But in their wake we can learn a lot about grace, a God of second chances and be the better for it."  By framing his infidelity in that light, Sanford made it difficult for any of his Republican opponents to attack him since, if they did, they would be attacking the idea of forgiveness and redemption.

3. Sanford is a talented campaigner.  Regardless of what you think of his moral character, Sanford is -- and always has been -- a very talented candidate. He is quite  good on television (watch the "forgiveness" ad above and you will see what we mean) and has a sort of disarming down-home charm that plays well in the Lowcountry district. Sanford also ran a far better funded and more professional campaign than Curtis Bostic, his opponent in the GOP runoff on Tuesday. As of March 13, Sanford had raised better than $400,000 for the race while Bostic had collected just more than half that.  Sanford's spending edge allowed him to be a continual presence on TV while Bostic struggled to re-gather himself after making the runoff two weeks ago.

4. The 1st district isn't social conservative territory. If Sanford had been trying to make a political comeback in the Upstate 3rd or 4th congressional districts, he almost certainly would have lost to Bostic. But, the 1st district is filled with country club Republicans who care about fiscal issues but recoil at the harder-edged approach on social issues of their neighbors to the north. Sanford fit that sort of Republican voter like a glove. Bostic, who boasted endorsements from the likes of former Pennsylvania Sen. Rick Santorum and James Dobson, didn't.

5. Sanford ran as the un-politician. Sanford's electoral appeal has always been rooted in the perception that he's not like other politicians. He limited himself to three terms in the House and, when he served as governor, he had an openly hostile relationship with the Republican-controlled state legislature.  In that light, Sanford's affair -- and the public flogging he took for it -- fit, in an odd way, into his overall political persona.  You can easily imagine a voter thinking: "This guy doesn't owe anybody anything if he goes to Washington. Heck, other politicians aren't even going to want to be seen with him." Given how voters feel about politicians these days, being seen as the turd in the political punch bowl is actually a good thing.