It seems that McCain has found his one fall-back response when dealing with any question that he deems tough. While some people have wondered whether he's pressing his luck with using this answer too much, I simply don't think that mainstream media will call him on this for fear of looking like they're attacking his military service.
That's why we need to re-frame McCain's refrain...
I'm obviously not the first one to have this idea, but I haven't seen the issue framed in a way yet that really truly turns McCains POW response into a negative for him. Mind you, there's a tricky line between attacking the response and his service, and I think that nuance is what is hanging most people up.
Here's what I suggest the response be, every time that McCain brings up his status as a POW as an answer to a question...
"It's understandable that McCain wants to talk about his honorable time serving his country 40 years ago, because in the time since then he hasn't accomplished anything in Washington except become the best friend of the lobbyists and corporate bigwigs."
This is the narrative that needs to be pushed forward, so that the media starts to associate the constant "POW" response with dodging answers.
If the McCain campaign tries to bring up a list of Obama's accomplishments during his time in Senate, that's a challenge you take. You simply line them up next to one another and say that in only three years Obama accomplished much the same as McCain in 35. If you want to be nice, you even say that McCain did help co-sponsor one solid bill with our great Senator from Wisconsin (McCain/Feingold finance reform), then promptly went out and exploited the loopholes in it.
This is the way to attack the overused POW response to everything (which is cheap and lazy) without attacking McCain's service itself (which is honorable). It needs to be done now.
Let's re-frame this issue now, and turn what he thinks is his unassailable strength into a weakness!