Palin stupid???? Maher on what is Bush doctrine?

I was watching Bill Maher and he was talking about how dumb Palin is and they showed a clip about the Bush doctrine. He was making fun of her because she didn't know or something. Ok I must be dumb also. What is the Bush doctrine? It just seems to me that the guy is really and I mean really really biased. It just seems like there are just as many Dems that could be made fun of but he just doesn't do it. My point is sure the guy is funny but he is someone that shouldn't be taken seriously.