The Obama campaign released its documentary on the Keating 5 scandal, which John McCain was directly involved in. I think the move is genius. You can analogize all the negative campaigning to a gunfight.
There’s Senator McCain (this summer) firing wildly. Obama ducks behind the bar. McCain continues to fire wildly. Everyone encourages Obama to stand up and trade bullets, but Obama stays in his spot. McCain runs out of bullets (he’s re-using old attack lines). Then, Obama stands up. BOOM. Keating 5.