In 2000 Gore won 42% of the white vote and 90% of the black vote. In 2012, Obama won 39% of the white vote and 93% of the black vote.
So at most, Obama got an extra 3% of the black vote on account of his race, and lost at most 3% of the white vote. So on the face of it, a wash. Of course, the white electorate is over five times larger than the black electorate, so that's really -2.2%, +0.4%.
Even if Obama had performed at Bill Clinton's historically low 83% of the black vote, his popular vote total would have been only 1.3% lower. This may have been enough to make him lose the popular vote, but it would not have been enough to make him lose the electoral college (Mitt Romney would have needed to win the popular vote by 3% to have won the electoral college).
So at most, Obama got an extra 3% of the black vote on account of his race, and lost at most 3% of the white vote. So on the face of it, a wash. Of course, the white electorate is over five times larger than the black electorate, so that's really -2.2%, +0.4%.
Even if Obama had performed at Bill Clinton's historically low 83% of the black vote, his popular vote total would have been only 1.3% lower. This may have been enough to make him lose the popular vote, but it would not have been enough to make him lose the electoral college (Mitt Romney would have needed to win the popular vote by 3% to have won the electoral college).