Nate Silver tries to answer the question: "How do people formulate their political beliefs?"

An important epistemological question that is, he says, under-discussed.

He lays out his theory:

I think political beliefs are primarily formulated by two major forces:

Politics as self-interest. Some issues have legible, material stakes. Rich people have an interest in lower taxes. Sexually active women (and men!) who don’t want to bear children have an interest in easier access to abortion. Members of historically disadvantaged groups have an interest in laws that protect their rights

Politics as personal identity — whose team are you on. But other issues have primarily symbolic stakes. These serve as vehicles for individual and group expression — not so much “identity politics” but politics as identity. People are trying to figure out where they fit in — who’s on their side and who isn’t. And this works in both directions: people can be attracted to a group or negatively polarized by it. People have different reasons for arguing about politics, and can derive value from a sense of social belonging and receiving reinforcement that their choices are honorable and righteous.¹

Notice what’s missing from my list? The notion of politics as a battle of ideas. This is not to suggest that people don’t hold reasonable moral intuitions about political affairs. But when it comes to mass popular opinion, the number of people who are interested in ideas for ideas sake is vanishingly small.