I don't buy what people are saying about the divisiveness in the Democratic Party. There's been so much talk about Clinton supporters who won't vote for Obama if he gets the nomination. Some even say that they'll vote for McCain if they can't vote for Hillary. Whatever.
After the 2000 and 2004 losses, I heard many folks talk disgustedly about moving to Canada. Didn't happen. There's a lot of emotion in statements like these, but I don't worry about a bunch of fellow Democrats getting all Canuck on me. Surely I can't imagine, after some time has passed between the upcoming Democratic nomination and the general election, that most Democrats who currently support Hillary won't be casting their vote for Obama. (Or Obama supporters voting for Hillary, for that matter.)
After a few weeks of grumbling, and letting it sink in that the losing campaign is actively endorsing the victor, the bad feelings will pass and the party will be united again. That's my take on it anyway.