Especially on foreign policy, this debate is deeply repetitive of the previous two debates, even though the questions are supposedly more diverse since they come from ordinary people (maybe that's because they were all screened by Tom Brokaw). For McCain it's that he opposed sending troops to Lebanon, that Obama opposes the surge, and that Obama wants defeat in Iraq (also sometimes that we need a surge in Afghanistan and Obama wants to invade Pakistan). For Obama it's that McCain supported the war, we have to end the war in Iraq, and we need more troops in Afghanistan (and sometimes he says McCain wants to invade Iran).
It's not that surprising that the candidates are trying to emphasize a few basic points -- it's what politicians do -- but given that the debate audiences must overlap significantly, it's kinda boring to repeat the same talking points over and over. I know most voters don't pay as much attention as I do, but I think they still must pick up how repetitious this debate has been on foreign policy. McCain is worse at making this repetition seem natural -- and that's one reason this debate won't help him based on what's come so far. Obama is better at repetition, but I think he could be a bit more spontaneous too -- would mentioning Maliki's support for his plan hurt? I don't think it would.