Yeah, It's somewhat speculation as to what the deeper motivations of large numbers people to vote for(or against) him were. I just find it interesting that so many call him the "black" president, and ignore the "white" half like it doesn't exist(incredibly some nitwits actually called Bill Clinton the first "black" president). I think it's due in some part to a desperate desire to prove the US isn't as racially divided as it is. 
I'm somewhat aware of the cultural history of slavery with it's tiered descriptions of racial mix, there were probably at least a half dozen categories IIRC. 
Like I said, his race has nothing to do with my largely negative opinion of him, was he better than Bush, sure. But that's such a ridiculously low bar...