My question would be, why didn't 95% of whites vote for Obama?
Anti-black racism in the white American community is ugly.
The African-American population has traditionally voted 85%-90% with the Democrats. Clinton, Gore and Kerry carried similar numbers. In the primaries, Obama was initially losing to Clinton 60-40 with this group.
There may an insignificant number of people voting for him because of his race, just as there are people who voted against him for the opposite reason.