As of now, Barack Obama is headed toward a monster win in South Carolina, the likes of which we haven't seen since, uh, 11 days ago. Dozens of news cycles ago, Hillary Clinton beat "uncommitted" in Michigan with 55 percent of the vote and a 15-point margin of victory. But there was a huge caveat: Nobody campaigned there and no delegates were awarded. It was a meaningless victory.
Flashforward to tonight, when Obama currently holds a 17-point lead over Clinton in South Carolina with 54 percent support overall. The victory is real this time, with actual visits from the candidates, actual delegates awarded, and actual names on the ballot. If the current results hold, Obama will have beaten his named opponents by a larger margin than Clinton beat her unnamed foes. This is probably making Obama's people giddy. Now whenever Hillary Clinton brings up a Michigan win (which she's doing more and more often as she tries to seat Michigan delegates), they can remind everybody that her win there wasn't actually that convincing and pales in comparison to Obama's Herculean display down South. Obama, the thinking will go, shows up when the stakes are high, while Clinton shrunk away at the first sign of competition.
Perhaps most importantly, Obama's win tonight moves the campaign from the plurality to the majority. The threshold for an impressive win has jumped from 40 points to 50-plus points, even with three competitors in the race. Winning the plurality of voters is a puny accomplishment—after all, somebody had to do it. This mini-thesis gets blown up if Edwards drops out of the race, but that's looking less likely after he secured some delegates with tonight's respectable showing.