Melinda Wenner wrote an articlethat appeared on www.livescience.com in which she reported on a study that suggests that there is some genetic predisposition for political philosophy. Here is a quote from her article:
People who are more conscientious and prefer order, structure and closure in their lives tend to be more conservative, whereas creative people who are open to new experiences tend to be more politically liberal, says John Jost, a psychologist at New York University who conducted an overview of previous studies involving a total of more than 22,000 participants from 12 countries.
The article points out that one psychologist believes that environmental factors or situations that people encounter in their lives determines approximately one-half of political preferences. Approximately 40-50% seems to be based in genetics, not so much that people are genetically inclined to be liberal or conservative, but that they are genetically inclined to have certain values or react to situations in a particular way.
This interplay of genetics and experience might explain why there are "conservative" Democrats and "liberal" Republicans. Their experiences lead them in one direction, while their genetic make-up leads them in a different direction.