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5 things to watch in the South Carolina special primary election

Voters head to the polls on Tuesday to select nominees in South Carolina's 1st District special election. A memorable field -- Mark Sanford, Stephen Colbert's sister, and Ted Turner's son are all candidates -- will be whittled down, and we'll get some fresh clarity about the race.

There's a lot to watch in the Palmetto State. Here are five things you shouldn't miss:

1) Who will face Sanford in the runoff? 

Two things are near certainties in the Republican primary: There will be a runoff, and it will include Sanford. The former governor, who fell from grace in 2009 after disappearing from the state and then admitting to an extramarital affair, is back on the political circuit. And his universal name recognition and fiscal conservative chops should be enough to propel him to the top of the GOP heap on Tuesday.

But Sanford won't likely hit 50 percent, and that would mean an April 2 runoff. Here's where things get interesting. Forget the field of 68, it's all about the field of 16 (!) competing for the GOP nomination. That's right, 15 Republicans are vying for a game of one-on-one against Sanford.

And it's anyone's guess who will advance, with virtually no publicly released polling and hard-to-predict turnout (more on that below).

That said, there are some leading candidates. There's Chip Limehouse, a long-serving state legislator who is well-known in the district and has emerged as the big spender on TV ads in the primary campaign. Teddy Turner, the son of media mogul Ted Turner, has also been spending substantial cash, according to his campaign finance report. Limehouse clearly believes that he and Turner are competing for at least some of the same voters, since he has gone negative against him.

A few others to watch: State Sen. Larry Grooms, who has courted tea party support, and has the backing of conservative Reps. Jeff Duncan and Mick Mulvaney. Lesser-known Curtis Bostic is also making a push for conservative voters. And former state legislator John Kuhn dropped $500,000 of his own money into the campaign as of late February, according to his campaign finance report. That alone makes him worth monitoring.

(For more, The Hotline has a detailed breakdown of the five likeliest prospects here.)

2) How many Republican primary voters will turn out?

Pegging turnout for an off-year primary election in March is equal parts guessing game and, well, more guessing. If turnout eclipses 40,000, then the better-known candidates -- Sanford and Limehouse -- will likely perform better. If it's in the 30,000-35,000 range, that's better news for lesser-known candidates. And if fewer than 30,000 voters turn out, then we could be in for a really wild night.

3) What share of the vote will Sanford claim? 

In a low turnout primary with a very crowded field, no one expects Sanford to dominate, which is why a runoff is pretty much a forgone conclusion to most observers. Still, it will be interesting to see his level of support, since this is the first time the former governor will have gone before voters since leaving office in 2011 under a cloud of controversy. Anything between 40 and 50 percent would be a very big showing for Sanford, but something in the 30-35 percent range is probably more realistic, given the circumstances of the race.

4) Elizabeth Colbert Busch is poised to advance. Then what?

Colbert Busch, the sister of "The Colbert Report" host, will almost certainly win the Democratic nomination on Tuesday. She has only one opponent, Ben Frasier, a former candidate who is viewed as an also-ran.

Colbert Busch has put up impressive fundraising numbers and, by virtue of her brother's fame, has won some valuable media attention. The question is whether that will translate into defying the strong conservative tilt of the district in the general election. Nearly six in 10 voters chose Mitt Romney over President Obama there last year.

A heated GOP runoff would be good news for Colbert Busch. It would give her a couple more weeks before attacks are lobbed against her, and would force the Republicans to expend more resources slamming each other. The special general election is May 7.

5) That other "R" word: Recount

All eyes will be on the GOP runoff, but in a really close race for second place, it's possible that Sanford won't know who his opponent will be when he heads to bed on Tuesday night. If the two candidates vying for the second spot in the runoff are separated by 1 percent of the vote or less, a recount will be ordered. It's not a very likely scenario, but given how unpredictable the election could be, it's at least worth bearing in mind as a possibility.