We've seen from the first debate that one of Bush's 5 talking points that he keeeeeeeeeeps on hammering (no matter the question), is that Kerry keeps changing positions. He responded effectively at the debate, but imho, we need to keep lobbing bite-sized comebacks at this.
My suggestion: "My values remain constant, they don't change. What I care about - safety, security, freedom (fill in this blank) - remains constant. But necessarily, our strategies sometimes have to change. Bush refuses to admit the need to do something different, when his strategy isn't working. But you can't expect to keep doing the same thing, but somehow start getting a different result."
Or something like this.
Can't wait to see Edwards and Cheney!