I think the GOP is under the illusion that, if they could just get credit for some sort of immigration reform and toss a brown person the ballot, they'd capture a significant portion of the Hispanic vote. They don't have a single issue like that to try to play against the black vote.
That's what McCain tried with his VP pick. Everyone knew that the US wasn't going to nominate another Republican after Bush and the race to the white house was going to be between President Obama and Hilary Clinton. Either way, history was going to be made and McCain was too much like George Bush. He wanted to spice it up and thought it would do something but it didn't work.
If it was Barack Obama vs Herman Cain, do you think Cain would have picked up a noteworthy percentage of the black vote?
Only black republicans would support him. It is taboo to be a black republican and I'm sure some of it has to do with "monkey see monkey do", but as the bishops said in the link that I provided in the other thread, you wont find a candidate that you 100% agree with. Democrats just seem to appeal to the struggles that affect the black community more so than the Republicans.
Now, to tie in both comments, if Sarah Palin were more appealing, I believe that she would have taken more of the women vote than Romney, same with McCain (assuming his opponent weren't black). People will vote for certain demographics, but I don't think they are completely ignorant to completely overlook every flaw. The candidates have to have some level of competency.