Whatever they do, they shouldn't dignify the lie with a major effort and emphasis -- that will ONLY reinforce that the lie is really a big issue that deserves attention. Bush will then be giving it life by what he is doing. Not good.
And yes, ignoring news leads on the alphabet networks is definitely a good idea when those networks are simply serving as a Kerry mouthpiece. You won't get them to change their tune...you'll only give them more fodder to pursue the story with.
I noticed that all the soundbites of Bush today were him talking about jobs and domestic issues -- that PERFECT for this time in the election. He's eating at issues now that are true upper midwest/heartland issues. He's going on what is assumed to be Kerry's turf (domestic) and taking it to him on offense. That's a great plan.
Remember too, that they didn't respond to the Rathergate/CBS fiasco either, and that turned out to be the correct action. Now Dan Rather and the New York Times have tried their bluff with a second card, and the Bush team is holding their aces, merely calling. When they play their cards, it will be to win.