Citizens are political simpletons--that is only a modest exaggeration of a common characterization of voters. Certainly, there is no shortage of evidence of citizens' limited political knowledge, even about matters of the highest importance, along with inconsistencies in their thinking, some glaring by any standard. But this picture of citizens all too often approaches caricature.

Paul Sniderman and Benjamin Highton bring together leading political scientists who offer new insights into the political thinking of the public, the causes of party polarization, the motivations for...