Looking towards November, Marc Ambinder outlines the important questions regarding Obama's weak support among white/rural/less educated/lower income Democrats.
"Are the demographics of Obama's coalition so skewed (in terms of previous coalitions) that his national lead will greatly overstate his relative strength in the electoral college? Or is Obama's new coalition so robust as to absorb some of the bleeding of white, working class men in states like Ohio and Pennsylvania and still end up winning?"
First of all, it is very important that Senator Obama never use a phrase like "the bleeding of white, working class men." But the critical question his campaign must address is how his "coalition" will translate to the electoral map. Here's one good discussion of the topic.