Every Republican is going to run on strong defense.

Every Republican is going to run on tax cuts.

Where McCain seeks to differentiate himself from the rest of the GOP field is by his efforts at censoring political speech, uh, I mean "campaign finance reform". That is the issue on which he defines himself.

So, as more and more people become aware that McCain is talking the talk, but not walking the walk, and hypocritically exempting his own constituency from the rules, it will be harder, if not impossible for him to run on that issue.