Obama gets more net votes because he's black
Obama gets fewer net votes because he's black
Obama's race has no bearing on who votes for him.
The number of people who vote for him is canceled out by those who vote against him BECAUSE of race
Questions that suggest blacks vote motivated by race is fair game. This does not and is divisive.
I think the people who wouldn't vote for him because he's black are generally the same as the people who wouldn't vote for him because he's a democrat. Would be far more interesting to see a black Republican candidate.