What I think we are seeing is a clash of the classes. I believe what is being interpreted as a racial divide, is actually a social divide.
Clinton's campaign is addressed more to the blue-collar worker, they feel oppressed and she is their savior, the only one "tough" enough to fight for them. It is the disenfranchised worker who is angry and wants to be reassured that things will get better. She promises healthcare and jobs, and that is their primary concern. They trust her to be aggressive enough, tough enough, to get the job done.
Obama's campaign plays better with the college-educated, white-collar workers. They are less concerned about healthcare and jobs for themselves, but more concerned that others have it.They are concerned with a dwindling middle-class and a loss of civil rights. These folks are looking for a change in how our government conducts itself in the global community, and how it treats it's own citizens.
What has got everyone so confused is that you can no longer determine social class by race or gender.