Here's what jumps out at me from the first wave of exit polls that have been released to the Edison-Mitsofky consortium:
Forget the horse race numbers for a moment: if the surveys are accurate, the polarization within the Democratic Party has reached critical levels. Nearly six in ten Obama supporters in Indiana say they would be dissatisfied if Clinton were the nominee -- that's (I believe) the high percentage of Obama supporters who have ever said that.
In both IN and NC, two thirds of Clinton supporters say they'd be dissatisfied if Obama were the nominee -- I believe that's the highest number recorded for that question, too.
The percentage of Clinton voters who say they'd choose McCain over Obama in a general election is approaching 40% in Indiana. Put it another way: in North Carolina, less than HALF of folks who voted today for Hillary Clinton are ready to say today that they'd definitely vote for Obama in a general election.
The basic demographic breakdowns suggest that the black/white split has widened as well (although I can't say too much about that now), which might mean that racial polarization (along with SES polarization) is driving the Democratic race to an unprecedented degree.