The McCain campaign’s insistent focus on the “celebrity” angle seems not only an effort to try to turn Obama’s strength into a weakness, but also a way to prepare the ground for his convention speech. The big stadium speech, in front of many tens of thousands, will no doubt provide a pretty impressive scene. The McCain folks, by trying to get the public used to thinking “empty celebrity” when they see Obama in front of a huge screaming crowd, seem to want to give some shape in advance to the public’s reaction to that image later this month. The opening images of the new ad out today make that especially apparent. It’s not a bad idea, and of course it helps that there’s truth to it.