McCain doesn't have to do a thing and Obama could implode on this issue alone.
Of course, the black church leaders of the Jackson/Shaprton ilk are sure to get all puffed up about the "racist" tilt. There are lots of respectable churches out there and if you are going into politics, people are going to ask about your church and you had better be ready with an answer. Obama's answers were lame and his recent "resignation" from the church looks like it was a reaction to the press reaction rather than a reaction to what was said in church.
McCAin doesn't need to do anything to win from this. The media will sling the mud and he just has to stand aside and not get splattered.