Indeed, Kerry may be cornered. If he repeats his lie, Bush can challenge it with the truth. If he speaks truth but contradicts his earlier statement, Bush can question him about the earlier statement.
Rove, Kerry analysts and GW's team told GW to just hang back in the first 2/3's of the debate and let Kerry say anything that he wanted to say. They probably knew that Kerry had gotten a preview of the questions before hand.
So Kerry was loaded for bear and spewed and spewed.
This was why GW look so poed while he listened to Kerry spew lies and other mantras.
Now those lies and mantras will hammer Skerry until the next debate. If he does the same tactic in the second and third debate, his mouth in the debates will have destroyed him.