One thing I noticed during the 2008 election was that events simply seemed to time themselves nicely for Obama - and that Mc Cain just sucked at everything.
Everything from the collapse of the markets to his mother's death - all fell nicely into Obama's lap from a timing perspective.
The one thing that Sarah has is the ability to disrupt this. She did it at the convention, she did it when she resigned, she did it with the death panels, she did it with her book, and she will do it again and again.
I suspect that Obama has already lined up a sequence of events in the lead-up to the next election that will favour him. That's why he couldn't care less about what's happening now, and about what he does or says - or what he rams through. It's all irrelevant because he's got a plan - and Sarah is the only one that can mess with that plan. That's why they want her gone.