Obama will be unlikely to disabuse folks over the next 60 days of an impression that has been decades in the making. All he will be successful of is reminding folks that McCain has been called "maverick" .. he may have more success painting Palin with the brush of "no maverick" but certainly not McCain.
I'm afraid this sounds pretty convincing. However unjustified McCain's maverick image is considering his massive sell-out these past couple of years, long-entrenched notions like that aren't going to be disabused now in two months. Especially not because you can rely on the gutless media to keep repeating the maverick shtick.
I think I've read a dozen times that negative campaigning only works when it plays on an already latent suspicion. Yes, you should attack the opponent on his signature strength, the Rove school of campaigning teaches us, but you have to do so by playing on notions that are already there.
So when Kerry's signature selling point was the war hero thing, you let the fringe attack those credentials head-on, but yourself focus on something that will undermine that strength, but does so by playing on already latent doubts. Kerry the feckless flip-flopper, the windsurfer, the dissembler. Eventually, entrenching the opportunistic flip-flopper and dissembler labels also serve to undermine the war hero stuff - did he fudge up some of that stuff too? Didnt he turn against his fellow soldiers once he got back home, only to play up his soldier credentials again 30 years on when he ran for President? Those are not my opinions, but that's how it worked.
In comparison, responding to McCains main selling schtick by just saying, "not so! not true!", when the shtick is one voters have been fed for years - I dunno, doesnt seem so promising.
Not that I've got ready-made answers on what to do...