John McCain said early on that Jeremiah Wright was off-limits. His campaign thought it was best to check, so they produced this ad (go to 1:13 for the ad):
Honestly, this is one of the more effective ads that the McCain campaign used. It is based on incorrect premises which undermine the entire Jeremiah Wright narrative, but it manages to tap into the technique used by the Obama campaign of sounding positive while pointing out the flaws in his opponent. While, I don't think it would have been a game changer by any means, it would have certainly been more effective than the various summer celebrity ads, and more effective than the entire Bill Ayres narrative. I would have been especially interesting in how the Obama campaign woudl have reacted. See Nate Silver's take here.