In the primaries, Dems vote along racial lines when the rubber meets the road. For example, when Mfume announced his run for senator to replace Sarbanes, he looked like a lock in a heavily Dem state. Mfume had served in Congress and was a past president of the NAACP. He was on paper an ideal Dem candidate. Instead, the Dem Party apparatus in MD frantically searched for a candidate and came up with Rep Cardin. Cardin won narrowly in a primary that saw voters voting along racial lines.
Obama was and is the token black candidate. He will meet the same fate as Chisolm, Jackson, and Sharpton. What will be interesting is if black Dems call in some chips and demand that Obama be placed on the ticket as VP given his showing in the primaries.
Obama has said he doesn't want to run for VP and who can blame him since Bill will be the co-president making the VP job even more worthless. However, the party may make him an offer he can't refuse. Obama has raised black expectations to a very high degree, so the party must do something to offset his defeat and not piss off their most loyal constituency.
Chris Rock has a monologue which serves as a reminder for why Obama will not be the VP nominee. He boldly proclaims he’d shoot the President if it would make a black man president (at the time, he seemed to be talking about Powell). He figured he’s spend life in jail, but would be a rule the prison as a hero.
He was joking, but some might take the point he made seriously.
Oh yeah... that and the fact that the Democratic Party would never let one of their slaves actually run the plantation.