Your suggestion makes me think Obama’s answer to that last question can be interpreted in different ways because it was indirect. I think answering a question of that depth first is why he wasn’t as clear as he could have been.

A more direct answer on his part would have made for a stronger conclusion, but maybe he meant it the way you say and it was just a verbal and mental disconnect.

McCain ended this debate better, but the end doesn’t really matter when you lose the beginning and the middle right?

Thanks for the comment.

He was not very clear, but his second sentence (after joking about his wife’s knowledge of his ignorance) was:
“But, look, the nature of the challenges that we’re going to face are immense and one of the things that we know about the presidency is that it’s never the challenges that you expect. It’s the challenges that you don’t that end up consuming most of your time.”
Then he went on to what he does know.
http://www.cnn.com/2008/POLITICS/10/07/presidential.debate.transcript/

I understood the message to be that what he doesn’t know is what to expect, what challenges he would face, the ones that will take up most of his time.
This is essentially the SAME thing that McCain then said, although McCain said it more clearly:
“I think what I don’t know is what all of us don’t know, and that’s what’s going to happen both here at home and abroad.”