This is the least of Hollywood's worries, for my money. The major studios have a bigger problem -- such as the fact that they so seldom make movies with serious themes or content. And they never address actual political issues if they can avoid it.
My suspicion is that no Hollywood producer is involved in the McCain presidential run. I say this for a simple reason -- it's badly orchestrated.
Every celebrity feels differently on the question of political advocacy -- whether a star should campaign for a candidate and whether that effort helps or hurts.