The NY Times has an interesting article by psychologist Jonathan Haidt that examines the behavior of voters.
To understand politics, we are often told to “follow the money”. Monetary self-interest is a good predictor for the behavior of politicians, but it doesn’t seem to help at all for understanding how people vote. Consider people who who are not very rich but nonetheless support tax cuts for the wealthy (e.g., Joe the Plumber). Studies have also shown that parents whose children attend public schools are not any more supportive of government aid to schools, and people without health insurance are no more likely to favor single-payer health insurance.
In other words, ironically and despite the gospel of capitalism, people are not always selfish. Instead, we evolved to favor the interests of our group or tribe over our own interests. These groups are often built around what are considered “sacred values” — if an outsider violates one of these values, the group springs to its defense.
This happens both on the right and the left. Recent examples include the right perceiving a “War on Christianity”, while the left perceives a “War on Women”.
UPDATE: The NY Times review of Haidt’s new book about this.