Obama's core premise for electability is his ability to appeal to all ethnic groups, all ages, all socioeconomic classes.

This is WHAT the Clintons are attacking.

They are using the race card because it's the easiest--it's most visible and has been used many times before (with success, regrettably).

The campaign needs to say, "There she goes again dividing the electorat." And leave it like that.

The more you say race, the more people repeat it, the stronger the case becomes.