For anyone who believes that the Democrats will unite as soon as they have a nominee, the Washington Post has a must-read piece on the lingering bitterness between the two camps.
It's been known for quite some time now that a sizeable -- and growing -- percentage of the Democratic primary electorate will not vote for the "other" candidate: Roughly a third of Hillary supporters have consistently said they would not vote for Obama, and a quarter of Obama voters feel likewise.
Conventional wisdom holds that the vast majority of these disgruntled voters will eventually make their way back to the nominee, but nothing has been conventional about this election so far. It's gone on much longer, and been way nastier, than anyone could have predicted, and how it impacts the Democrat's ability to unite is a big X factor.
Given that McCain is saddled with a wildly unpopular President in a change election, the only chance he stands is if the bitterness lingers into the general election, and he takes advantage of it by appealing to Hillary's coalition of blue collar workers, economic populists, and church-goers (the Reagan Democrats). McCain would be smart to tear a page from Hillary's playbook and stick to the issues they care about: economic security, values, and experience, and leave the foreign policy stuff on the sidelines. It probably goes against his best instincts, but it could be a winning formula.