While I think the "Celeb" moment has been incredibly useful in throwing up a cloud of dust in Obama's face and putting him on the defensive, I don't think it's anywhere close to what McCain's closing argument should be. Ultimately, it's attacking Obama for his popularity, and popular isn't a bad place to be.
Where McCain twists the knife is on Georgia.
Georgia is where McCain highlights the necessary flip side of Celeb -- Obama's naivite and inexperience. Part I of the narrative is that Obama is just a rock star who packs stadiums. Part II is that rock stars don't solve your problems.
The Georgia/Russia crisis is the reason why Americans have elected Republican Presidents for 28 of the last 40 years, even if they lean a little to the left on domestic issues. In a time of crisis, you need a hard-headed, tough leader who will have his eyes wide open on foreign threats. McCain, a long-time Putin critic, is perfectly suited to that 3 AM role. In a thumbnail way, Obama is the least-well-suited Democratic candidate on this score since McGovern.