It wasn't Obama, it was the Democrat thing. Most Democrats will vote for a yellow dog or a black dog with enough encouragement by the disinformation industry (AKA the Press) and other Democrat.
And not understanding the Democrat mind is the Republicans' greatest failure. And that failure is what played a big part in putting Obama in the white house. Remember, Obama was at first struggling to get traction, and then the Clintons came to his political rescue by reminding the Democrat base that Obama was a Democrat, regardless of his color, and could be counted on to do all the crooked stuff expected from Democrats.
To understand the Democrat mind Republicans have to understand the Clintons and why they are so popular with Democrats. Bill Clinton was never admonished by Democrats for his little Oval Office romance with "that woman", nor with the other women, or for the dozen of other things he did that would get a Republican thrown under a white house bus. Just the opposite, he was praised and envied for what he got away with. For Obama to get elected he had to overcome that crap about there being but one America that he mouthed 4 years earlier, and act like a Democrat. It also helped that John McCain helped him get elected by pretending that Obama wasn't just another Democrat. That Republicans nominated McCain to run against Obama pretty much confirmed then that Rinos were in charge of the Republican party.