Kerry vs. Edwards. The "liberal" Northern candidate versus the "moderate" Southern candidate. It was the regional matchup everyone expected, even if the route and the names of the candidates didn't gibe with expectations.
The bottom line? It's a new contest. Kerry is about to find out what Dean realized was a difficult task -- running a 50-state race, running against Bush, facing attacks from Democrats, Republicans, and rumor mongers, and maintaining the "aura of inevitability" all at the same time. while Kerry has the clear upperhand at the moment, nothing is inevitable at the moment.
Edwards, on the other hand, can cherry pick his battles. He was able to move into Wisconsin and campaign hard for his well-earned strong second-place showing. Kerry was wasting time in Nevada and its beauty contest caucus. Yet the demands of that "50-state" race dictated Kerry spend time every place that votes. Or maybe that was just a really dumb decision (like Dean's Georgia visit on Iowa's eve).
But ultimately, Kerry's biggest weakness is that no one likes him, unlike the well-liked, charismatic Edwards. The exit polls have been clear -- people vote for Kerry not because they are inspired, agree with his policies, or otherwise find him an attractive candidate. They vote for him because they think he is "most electable". And that aura is fading. The attacks are taking a toll on him and that perceived "electability". And since his support is not deep, it's artificial and thin at best, he has nothing to fall back on.
On the other hand, Kerry has a big delegate lead. And given that states are no longer winner-take-all, Edwards would have to start winning with BIG margins to start making up that 400+ delegate difference.
But the mo' is on Edwards' side. It'll be interesting catching the next round of March 2 and national polling to see if Kerry is holding steady or suffering any erosion in his position. Edwards' ability to close is spectacular (and should be considered legendary if he can keep it up), so Kerry will need as much distance as he can muster. Because with Dean out of the race, Kerry doesn't compare too favorably with Edwards.