Rigged because they will actually face tough questions? vs the normal Presidential "debates" where Obama's buddies in the news media will toss him softballs?
rigged because questions are planted and questioners are selected ahead of time. there was a blog on this about someone in one of the ohio debates being chosen to ask mccain a question. its all a glorified pep rally essentially.
now if you get it on neutral ground then lets play lets play. until then though you'd be an idiot to accept one of them.