I think McCain does need a knock-out, even a TKO.
He needs to hammer Obama on Fannie Mae, Ayers and Wright and not settle for the inevitable passing dismissal from Obama. He needs to make Obama: A) crack and lose his temper or B) be shown to be so evasive/lying as to be transparent.
He needs to do this precisely because The Comiteriat is writing the news. It has to be so obvious that Matthews, Olbermann and the rest can't dismiss it either. Sure, they'll call it racism etc but if it is obvious enough the indies will see past all that.
McCain needs to hit and hit hard. Obama's camp is refusing to answer direct questions, now it's time to hit Obama himself. He will evade, he will prevaricate, he will outright lie; but he cannot under any circumstances be allowed to get away with it on national TV because the viewers are not going to follow-up on the internet tomorrow.