If he's in coalition with them what better position to be in than to have the power and influence, and be able to tell people what he thinks about them!  I listened to Cameron on radio 4 when they were putting aspects of the NO campaign to him, especially the dead baby poster, and all he'd say was that he wasn't in charge of that campaign, but still wouldn't say it was wrong, and even backed it up!  No wonder the libs felt stabbed in the back.