Obama's mission tonight is to put on a C+/B- performance. Just maintain the status quo. Don't take any risks attacking Romney, but make sure he doesn't put you on the canvas
No way. Obama has to convince people that Romney is the douche all of his ads say that he is. If that image dissipates, Obama is in a world of trouble. It is the only thing keeping him afloat.
Dukakis did not lose because of Bush's Willie Horton ad; Dukakis lost because his answer on the death penalty question reinforced the accusations made in the ad (in the name of being fair and balanced, it is worth noting that Dukakis was overcoming a cold [or flu, I forget which] at the time, which is a little known fact). Bush and Co. ran the same attack ads on Clinton, but they failed to seal the deal in the debates, which is why the attack ads did not work as planned (as is the case today, not many people in 1992 wanted four more years of the last four years).
If Obama is hoping to win because of his negative attack ads, he needs to ensure the debates reinforce the image painted of Romney in those ads. Romney is almost certainly not going to do himself in like Dukakis, so Obama has to do it by selling people on the attack ads. Given his political prowess, if anybody can do it, it is Obama...