It's not a hard question.

Define 'honor,' Senator McCain.

JM: Read it in my books.

Time: I've read your books.
JM: No, I'm not going to define it.

Time: But honor in politics?
JM: I defined it in five books. Read my books.

Going down to brass tacks, this is probably the result of the campaign (that John McCain does not speak for) having words with John McCain to start speaking for it. Thus, McCain takes no chances now, and is clearly irritated by that.

But how hard is it to define "honor"? If he really knew what it meant, and if he believed in it as more than a nice decorative ribbon atop his former Prisoner of War status, he would have no trouble defining it. The trouble is that his campaign has not taken an honorable stance as anyone could possibly see it, and so he knows that if he goes that route, he'll be trapped into categorizing his campaign's tone.

As the campaign creaks onward, John McCain is going to be more and more limited in his responses. No one on his side wants another "houses" fluff (which was ironically made because he probably felt he had to defer to his staff on everything). Thus, I'm sure McCain is going to become crankier and crankier as he's caught between what he wants to say and what he thinks his campaign wants him to say. He won't have the acuity to stay on message and speak off the cuff at the same time. I'll be very surprised if we don't see some minor meltdown at the debates, even if all the questions are framed in his favor.