Yesterday, we took a look at plausible Florida scenarios. Today, it's on to South Carolina, where Democrats vote tomorrow in what has become the nastiest, most personal primary on the Democratic side so far. What if Barack Obama, Hillary Clinton or John Edwards wins here? Let's take a look:

Barack Obama: Like it or not, race has become a factor in South Carolina, and it may have broader implications for the rest of the contest. Obama scored a big win among African Americans in Nevada, while losing Whites and Hispanics. If Obama wins by a wide margin in Palmetto country, it will be thanks to a large portion of white voters who backed him as well. If he manages a small win, it will be largely because of African American votes.

A big win shows Obama can attract southern Whites. That would seem to forecast victories in other Southern states that vote February 5, including Georgia and Alabama. A narrow victory might be trouble, and in light of that, Obama may focus his Super Tuesday attention on Northern states. A loss, which looks unlikely, will by no means signal the end of the Obama campaign, but could further the perception of a race-based contest. That, in the end, is good for none of the Democrats, who will need Clinton and Obama standing side by side -- whichever ends up as the nominee -- by convention time.

Hillary Clinton: Winning South Carolina would be a huge upset, which Clinton seems to be good at lately. No one expected her to win New Hampshire, and she almost pulled out of Nevada before making a comeback there. South Carolina would be even bigger, and would fuel the media's renewed obsession with her as the front-runner.

But the only way Clinton wins is by tapping a significant number of African American votes. Bill Clinton is widely popular, still, among black voters, and if she is to pull off a victory, it will be largely because of his focus on the community in the last few days. Politics is a zero-sum game: Every black voter who casts a Clinton ballot is not casting an Obama ballot. If she comes anywhere close to Obama's numbers among African Americans, expect the campaign to spin it as a big victory, even if Obama pulls more votes overall.

John Edwards: Recent surveys have shown Edwards on the move in South Carolina, his native state. But it may be just too little, too late. Edwards needs the state more than anyone else, and it looks increasingly unlikely that he'll get a win. To do so, he'll have to pull heavily from both white and black voters. A win, or even a good showing, would send a strong message: Populism isn't dead. That's good news for Edwards, but he doesn't have the money or the time to spread it among February 5 voters.

South Carolina will not likely end anyone's campaign, though it may end Edwards' hopes of being president. For Obama and Clinton, the state is the last opportunity to win delegates before February 5 -- the DNC stripped Florida of its delegates, which were to be awarded on January 29 -- but it is by no means make or break for either.

Obama will likely get the momentum of a win, but the question remains: Will it be enough to propel him to a Super Tuesday win? The Clinton camp should still be worried about damage it has done among African American voters, though exit polls tomorrow will show how bad those injuries are. And Edwards needs to begin to think about what comes next, a gallant but probably futile charge toward February 5, or a graceful hunkering down to decide which of the other two deserves his support.