This study http://www.sciencedaily.com/... says that on average, smarter people are more likely to be athiests and liberal. Smarter men are also more likely to be monogamous apparently.
This information is not causal. It could be that smarter people feel like they need to be liberal as a signal to other smart people of how smart they are. On the other hand of course, it could be that these really are just the smart choices.