Exit Poll Breakdown

You can go here to read a summary of the exit polls from last night's Democratic presidential primary in Pennsylvania. Hillary Clinton decisively defeated Barack Obama, but not enough to make up serious ground in the delegate contest. By all accounts, she still needs to win essentially 70% of the popular vote in the remaining primary states to catch Obama in the pledged delegate total. That is an unlikely total, but the size of her victory in Pennsylvania allows her to sell superdelegates on the idea that she can best compete in big states (i.e. Ohio, PA, NY, CA, TX, FL).

For Obama supporters, this is the most worrying piece of news from above referenced article and it is what Clinton will remind superdelegates:

If Obama does win the nomination, a quarter of Pennsylvania Democrats say they'd either support John McCain or sit out the contest entirely; if Clinton's the nominee,one in six said they'd either vote for McCain or sit it out.

Is Obama's support too shallow to win in November? How real is this threat of Democratic defections in November?