What Obama should've done is come out with a wooden chair, set it in front of his podium, and walk off. When the empty chair debated Clint Eastwood it at least landed some pretty good jabs at Romney, and most of the press declared it the winner, or at least declared Eastwood the clear loser. An empty chair would've put Romney in the unenviable position of having to fill in both sides of an unscripted conversation and he would've been the one hemming and hawwing while he pretended Obama was replying to his points. Everyone would've come away from the debate thinking Romney had lost his marbles. I'm not sure how well Jim Leher would make Romney spend equal time pretending to listen to the chair, but if the press called foul it would paint Romney even more unfavorably.
Eastwood was definitely on to something, but Obama's campaign advisors failed to capitalize on it.