Democratic states have periodically been threatened by demagogues -- political figures who fashion themselves as leaders of the people but in fact use the levers of government to establish autocratic rule. In this intriguing book, Signer explores the intellectual and historical aspects of this old and troubling danger. A political theorist by training, Signer frames his inquiry around the insights of thinkers -- Aristotle, Thomas Jefferson, Alexis de Tocqueville, Leo Strauss, and Hannah Arendt -- who grappled with the sources and the fragility of governance by the people. Along the way, the book offers portraits of some of history's most infamous tyrants, including Cleon, the ancient Greek general; Adolf Hitler; Benito Mussolini; and such petty demagogues as U.S. Senator Joseph McCarthy and U.S. General Douglas MacArthur. Signer argues that the ability of democracies to resist demagogues hinges not on economic conditions or the design of institutions but on "the people" and whether or not they possess "constitutional conscience." In this sense, the book echoes Tocqueville's contention that liberal mores and traditions within society are the bedrock of democracy. Signer ends with some sensible suggestions on how the United States might help cultivate constitutional values in countries undergoing democratic transitions -- especially engaging civil-society groups and promoting education and development. But he does not really establish the claim that outside states can make a difference.