Election Day in South Carolina is here!

(Rainier Ehrhardt/AP)

One of the most memorable campaigns in recent years comes to an end today, with voters headed to the polls for the 1st district special election between Mark Sanford and Elizabeth Colbert Busch. Polls close at 7 p.m. ET. We'll have news for you over on Post Politics and analysis right here on The Fix once a winner is called. And for on the ground coverage throughout the day, follow our Post colleague Karen Tumulty. In the meantime, below are five of the keys to the race. What did we miss? The comments section awaits!

1. Will Republican base voters come home or stay home? We've written time and again about how Republican this district is. Mitt Romney won 58 percent of the vote in the 1st in 2012. There has not been a Democratic congressional representative in decades. We could go on. The fundamentals clearly favor Sanford, but to win the former governor needs the Republican base squarely behind him. Through a barrage of negative ads about his ethics woes and extramarital affair, Democrats have given GOP voters -- particularly women -- ample reason not to vote for Sanford. Even if they aren't sold on Colbert Busch, they may opt to stay home. But in the last week of the race, Sanford has regained his footing. He rallied the support of the state's two senators and the governor helped him raise money. Strategists in both parties say that he has the momentum and if that carries though to today, it will mean trouble for Colbert Busch.

2. African American voters: Colbert Busch is going to win the black vote by a wide margin. But just how wide that margin is could mean the difference between winning and losing. Sanford carried 22 percent of the black vote in his 2006 gubernatorial re-election race, and his outreach this time via urban radio advertisements suggests he thinks he can peel off more of the black vote than a typical Republican candidate. If Sanford's percentage of the black vote is in single digits, it's bad news for him. But if he can carry a double-digit percentage of the African Americans, it bodes well for his chances.

3. Berkeley and Dorchester Counties: This is very GOP-friendly territory that makes up about 40 percent of the district. (The 1st has five counties in total.) Sanford needs strong turnout and a clear margin of victory here to win. If turnout here is under 30 percent, it will be good news for Colbert Busch. If it is much higher, then it's a good sign for Sanford. Sanford will likely need to pull 55 percent of the vote in Berkeley and Dorchester counties, while over in Beaufort County, Colbert Busch will be looking to hit a similar mark.

4. The possibility of a recount: It's happened before, as recently as March on the Republican side, in fact. Given how close this race looked headed into Tuesday and how unpredictable turnout is, a recount is possible. For one to be triggered, the victor's margin would have to be less than one percent of the vote. It's not likely but it's still something to keep in mind if the race remains close late into the evening. And for political junkies, it would mean at least a few more days of Sanford and Colbert Busch in the headlines.

5. The post-game spin: No matter who wins, the losing side will have some explaining to do. Republicans would have the burden of carrying an embarrassing loss in an overwhelmingly GOP district and having to field more questions about why the party keeps nominating flawed candidates. A Colbert Busch loss would mean national Democrats spent big money but still came up short. And even winning won't be all roses. Republicans would be expected to heavily contest the seat next November if Colbert Busch is victorious. And if Sanford wins, it means the GOP conference will have an ethically challenged member in its ranks.