McCain's focus on Obama's "celebrity" seems to be coopting the campaign song I once suggested for Joe Biden, "New Kid In Town", a song is in the voice of somebody who is past his prime. Heck, it's even about a guy named (albeit figuratively) Johnny.
You're walking away and they're talking behind you,C'mon, John, you used to be happy to play up your status as a political celebrity. If you drew a crowd of 200,000 to one of your own speeches, you would justifiably crow about your accomplishment.
They will never forget you 'til somebody new comes along.
Where you been lately? There's a new kid in town.
Everybody loves him, don't they?
As much as people want to claim that this isn't really McCain's authentic voice, that he's uncomfortable with the low road, for now it nonetheless is his voice.
Update: Another round of McCain's tactics being "out of sync with the real guy".