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Alford, Funk, and Hibbing. 2005. Are political orientations genetically transmitted?. American Political Science Review 99 (May).

Main Point

Political attitudes (but not party ID) are more strongly influenced by genetic factors (interacting with environmental factors) than by environmental factors.

In (earlier) studies of religiosity, genetists have found that religious views/practices are strongly influenced by genetics, but religious affliation is not; it is simply learned from one's parents. Similarly, political attitudes are strongly influenced by genetics, but party ID is not.

Nature vs Nurture

The authors stress that environmental factors still matter; people can act against genetic predispositions, and genes most likely interact with the environment. For example, geneticists have found a specific gene that is related to depression--but it only causes depression when it interacts with high-stress events. Genetic predispositions most likely interact with environmental factors in similar ways.

Causal mechanism

Not especially clear. They talk at one point about an example that might summarize their view: Genetists have shown that genes influence a few general personality traits, like openness. Perhaps those with the "openness" trait are more open to gays, hippies, atheists, communists, etc--so that this trait reinforces liberalism.

Method

Large-N comparison of monozygotal and dizygotal twins.