Its tough to find actual early primary polls still posted from 8 years ago, but I followed the election closely and like most people paying attention saw that Obama grabbed the black vote from Hillary "overnight" in political change terms.
Also, its well established that Obama got a higher % of the black vote (already quite high) and a greater jump in raw numbers of black people voting for him than any other Dem before him. The 2004 to 2008 jump in % turnout among blacks was more than twice that of any other group. Given that chronic non-voters tend to be among the least informed, odds are high that the extra blacks that felt motivated to vote for the first time in 2008 were not compelled by knowledge of his policies as better than prior Dems that didn't vote for, but by his race.
Bottom line is that some people vote with race as a deciding factor, and unless black people are a unique sub-species, this also applies to them. That makes it beyond reasonable doubt that he got some % of black votes for being black (and lost some % of white votes for being white). Also, as I said, it likely mattered that Obama was not merely black, but black at a time when zero blacks had gotten close to the Presidency. It is highly likely that some people chose him over Hilary for that historic and symbolic reason.
Sure, no women has won it either, but lets be real, the historical symbolism of a white female president doesn't come close to that of a black president.
And as conservative as black people are, getting us to vote in significant numbers for the party of the Southern Strategy, Jesse Helms, and Willie Horton will take a lot more than fielding a black candidate.
I agree that this is true of the majority. But "significant numbers" is rather vague. Voters tend to be highly emotional and not well reasoned or grounded in historical understanding. Again, that is true of most American voters, which includes black voters. Older Blacks that experienced the Southern Strategy and Jesse Helms are far more likely to reject any GOP choice, but people under 35 could quite plausibly find a way to delude themselves that the only black choice was an acceptable one. If Obama had not already won in 2008, many people would still be doubting that a black person would ever win in their lifetime. So, a black Republican in a general election could easily get 10%-30% of the black votes.
In fact, 1992, Colin Powell was a Republican campaigning for Dole and other Republicans. Exit polls showed that he would have kicked Clintons as 50% to 38%, with many left leaning independents voting for Powell over Clinton, including 1/3 of blacks.
