How conspiracy theories explain political parties

After Cass Sunstein co-wrote bestseller Nudge on behavioral economics with Richard Thaler, he went on to run the White House Office of Information and Regulatory Affairs from 2009-2012, acting as the President's top regulator.

But some of his more curious — and controversial — research is on conspiracy theories: how they work, and why they're often rational for people to believe. His new book, Conspiracy Theories and Other Dangerous Ideas, details this research. He spoke with Ezra Klein on his theory, and how it helps explain the disagreements between our current political parties.