In psychology, projection is a well known defense mechanism by which the person project onto another person feelings that are actually inside of him. So if person A is angry and frustrated, he'll perceive person B as being frustrated and ask him: "Why are you angry?". This defense mechanism is widely used because it is very effective in dodging responsibility and lower anxiety.
I think that's what is happening right now in the McCain campaign, especially McCain himself. There is no rational reason for McCain to want to kill Palin's career. He know he'll never run again for president so they'll never compete together if she decides to do so. But it's easier for him to project his own feelings of anger and inadequacy on her than to face the reality that he made the choice to take her as a VP without proper vetting and he ran one of the worse campaign in recent American presidential history. That's why McCain snubbed her during the campaign, why he is probably encouraging (or at least not discouraging) leaks on her and why he'll never defend her again now that the presidential race is over. He'll use his projected anger on her as a rationale for categorizing her as a "bad guy" to help justify to himself his sinking of the Palin ship
As for McCain's aide, that defense mechanism is probably also in play although they do have a career incentive to sink Palin as low as they can (those that didn't help chose Palin that is). This will allow them to avoid blame for the campaign's failure: "I did a great job in the McCain campaign, but unfortunately there was nothing we could do with a VP like Palin and a crumbling economy. So you should hire me even though the last campaign I worked in was an abject failure.".