McCain runs a real risk of getting politically embarrassed by Palin becoming more of a draw at his events. You see lots of people in the audience waving "McCain Palin" signs. What if this got flipped and people started showing up to his events with "Palin McCain" signs?
I think this would become an embarrassment to John McCain and would actually become a big story. If some 527 group was to print up a bunch of these signs and start passing them out at rallies where McCain and Palin were appearing together it would take advantage of the weak popularity of McCain and the celebrity of Sarah Palin:
I think this could actually hurt John McCain to have him need to explain why his VP choice is more popular than he is. This could have the effect of causing them to split up on the campaign trail. If McCain and Palin are divorced on the trail and Palin keeps drawing bigger crowds than McCain it would be even more embarrassing.
I could see McCain getting really testing when reporters keep asking him why Palin is more popular.