TNR's John Judis looks at the exit polls and gets to the nub of the matter, not just for tonight but for the campaign for the rest of the year:
while Obama has clearly caught up to, and perhaps passed, Clinton in the battle for the nomination, they continue to have complementary strengths and weaknesses. To win in November, Obama is going to have do much much better among the white working class--one can assume that he would get Clinton's female voters just as she would get his African American voters. Clinton, on other hand, looks very shaky among white men. There remains a question, too, whether the young voters and independents who have flocked to Obama's banner would vote for her in the fall.
This seems a drily charitable view of Clinton's chances (I suspect Judis would vote for Obama, though elements of Edwards' agenda might also have appealed to him). It seems highly unlikely Hillary can do well amongst white men in November. Equally I suspect that many of the young voters flocking to Obama (an admittedly flaky, unreliable constituency) will stay at home if Hillary is the nominee. That would, admittedly, be evidence of inertia rather than an obvious anti-Hillary sentiment, but there you have it.