… is from page 115 of my colleague Bryan Caplan’s great 2007 book, The Myth of the Rational Voter :
Although initially jarring, it is coherent to assert that people are rational in some areas but not others. Irrational beliefs probably play a role in all human activities, but politics makes the “short list” of areas where irrationality is exceptionally pronounced. Furthermore, basic economic theory – properly interpreted – helps define the boundaries of rationality. Political irrationality is not an ad hoc anomaly, but a predictable response to unusual incentives.