Republican Mark Sanford has closed the gap with Democrat Elizabeth Colbert Busch in the South Carolina first district special election to take place on Tuesday. The latest poll from Public Policy Polling (PPP) has Sanford jumping into to a 1 pt lead 47% to 46% after being down in the same survey 9 pts just two weeks ago. A poll from Red Racing Horses (RRH) has Colbert Busch and Sanford tied at 46%.

A Sanford win in the final two weeks after being down 9 pts would be unusual. As I noted last week, only a little less than 15% of special election polls taken in the final two weeks of a campaign over the past decade have had a 9 pts or greater error margin. Even in the quick changing special Massachusetts senate election of 2010, Scott Brown gained only 4 pts in the final 10 days.

It's not as if voters all of a sudden like Sanford, the former South Carolina Governor who is most well known nationally for cheating on his wife. Sanford's less liked than Colbert Busch with a 43% favorable rating compared to 50%, respectively, per PPP. They just dislike President Obama. By a 4 pt margin, though, voters have a higher opinion of Sanford than President Obama. That reflects a district that voted for Republican Mitt Romney by 18 pts.

Therefore it shouldn't be surprising that Sanford's comeback is entirely built upon newfound Republican support likely gained by nationalizing the race. Some Republican voters are deciding that they would vote instead of staying home in disgust of Sanford's affair and divorce. The electorate PPP now projects voted for Mitt Romney over President Obama by 13 pts versus a projected electorate of just a 5 pt edge for Romney in their last poll. Sanford has also expanded his lead among Romney voters from 49 pts two weeks ago to 61 pts now.

The good news for Colbert Busch is that most of Sanford's comeback occurred about a week ago. You'll note that RRH conducted their poll in the beginning to middle part of last week, while PPP's was done over the weekend. Despite the differences in timing, the results are almost identical. That tends to indicate that Sanford has likely leveled off. The result is a race that is at this point simply too close to call with neither candidate having too much momentum.

So just how long will we have to wait for results on Tuesday Night? We should know by 9:30pm, if the primary for this election is any guide. The polls close at 7pm EST. During the primary this year, it took about 45 minutes (7:45pm EST) after the polls closed for results to start being reported. By 8pm, about 5% of precincts had posted their results. By 8:35pm, 50% of precincts were in. By 9:20pm, we had results for all but 1% of precincts.

Where are each of the candidates supposed to do best? The district is made up of five counties: Beaufort, Berkeley, Charleston, Colleston and Dorchester. In the 2012 house election for this seat, Republican Tim Scott got between 60% and 65% in all the counties except for Colleston. Colleston, however, makes up less than 1% of the district's population.

The RRH poll forecasts that we should see greater differences between the counties in this election. In their poll, which had a tie, Colbert-Busch led by 4 pts in Charleston and 13 pts in Beaufort. Sanford grabbed a lead of 13 pts in Dorchester and 20 pts in Berkeley.

Usually this county breakdown would be bad news for Colbert Busch given the populations each of these counties make up in the district. The issue for Sanford is that some voters the more culturally conservative areas in Dorchester and Berkeley seem to still be staying home. That's why we're expecting to see an electorate that voted for Romney by 13 pts, not 18 pts. If these counties vote their population weight, Sanford likely wins by 3 to 4 pts.

Thus, the key for Republican Mark Sanford winning is either high turnout or over-performing the expected county breakdown. Whether or not this occurs is what will determine either Sanford or Democrat Elizabeth Colbert Busch wins tomorrow. © Guardian News and Media 2013