“12 years ago a black GOP female candidate came within 6 points of McKinney”
But in 2012 the GOP has an excellent black, female conservative Republican running in GA-04: Catherine Davis. http://www.catherinedavis4congress.com/ It would take a miracle for her to win the general election, especially with Obama on the ballot increasing black turnout in that district (Davis would need each of Hank Johnson and Cindy McKinney to get between 30%-33% and get 34% herself, in a district that, as redrawn, gave McCain less than 20% IIRC), but at least our odds of winning are not 0% anymore.
I just realized that in all GA elections (except for the presidential race) there is a runoff in early December if no candidate gets above 50% (which you may recall occurred in 2008 in the Senate race between Saxby Chambliss and Jim Martin). So even if Johnson and McKinney split the Dem vote evenly and the GOP nominee (which won’t be Catherine Davis, since she’s not running) finished first with 34%, there would be a run-off between the top two finishers. Sure, turnout in the runoff would be a lot lower, and the electorate would be a bit less Democrat, but there is no way that a Republican (much less a white Republican) will beat either Johnson or McKinney one-on-one in that district.