UPDATE, 8:23 p.m.: Well, it's basically over. Beaufort County, the Sanford soft spot, went for him by a 6-point margin—2,152 votes. Charleston County is tied, when Colbert Busch needs to be winning it.
So, basically: Mark Sanford (R) defeats Elizabeth Colbert Busch (D), 54-45 percent.
UPDATE, 7:43 p.m.: Having stopped very briefly into the Elizabeth Colbert Busch party, and finding a classy selection of mostly-white Democrats enjoying a soft jazz band, I drove over to Sanford's party at Liberty Tavern in Mt. Pleasant. By that time, we'd received results from two counties: Four precincts in Berkeley (Sanford by 7 points so far) and all of Colleton (Sanford 70-29 over ECB.).
But about Colleton and its sole precinct here, Edisto Beach. In 2012, it went for Mitt Romney by a landslide, 496-160 votes. Sanford has won it 272-114. Instead of netting the usual Republican 336-vote margin, it went for Sanford by 158.
Original post, 6:31 p.m.: I'm deadly serious about Diet Vanilla Coke sponsoring this race. Publix had a good deal on the swill, and a 12-pack has powered my rough way across this district all weekend and week. More importantly—hey, it's election night! At 7 p.m. EST, the polls close across the first district of South Carolina. The AP will post results here, by county.
"But, Dave," you say, "I don't know anything about counties in eastern South Carolina."
Oh, it's easy. The new first district encompasses most of Charleston County—around 40 percent of the district, and swing territory, but good for Democrats. (The very most Democratic part of the district has been gerrymandered into Rep. Jim Clyburn's safe seat.) To the south, the next population center is Beaufort County. Sanford has roots there, but in the Republican primaries, he lost it. For Democrats to win, they need to make the rubble bounce in those two counties, because Berkeley County (Charleston suburbs) and Dorchester County are reliably Republican. (Colleton County only has one precinct in the district. If these were the five regions of Scotch whisky, Colleton would be Cambellton.)
One wrinkle: Both Berkeley and Dorchester have sizable black populations, more than a quarter of the population. Democrats did their level best to drive up black turnout—as much as they could without Barack Obama leading the ticket. How will we know if it worked? Well, in the close 2010 gubernatorial election, Nikki Haley won all of Berkeley by 17 points and all of Dorchester by 18 points. If it's any closer than that, bad for Sanford. (She won Beaufort by 20, so if that vote returns to Sanford it's basically over.)
What else to watch? Some social conservative leaders had talked about writing in non-Sanford names, spoiling the ballot, making a statement. That campaign, such as it was, appears to have died down as Sanford's looked more electable and started hypnotizing everyone with visions of a Pelosi speakership. But watch the vote to see if there's any drop-off bigger than statistics can explain. I'll be whizzing around the city and its election parties, so many of my updates will come on Twitter. Assuming nothing insane happens, we'll have a count that ends in a few hours, and I'll have a longer take in the morning. But why assume that nothing insane can happen?
Oh, and ECB says that Stephen Colbert will miss the party because "he has to earn a living."