No doubt many people voted for him for that simple reason. However, 90-plus percent of the black vote goes to the Democrat in every national election. If Obama had been a Republican running against a white Democrat, personally I’m convinced that 90-plus percent of the black vote would’ve gone to the white Democrat.
It’s the difference between 88%(Kerry) and 96% (Obama). That’s actually significant, but not determinative. It’s enough to create more of a gender gap than there really is.