How Democracies Die: The International Bestseller: What History Reveals About Our Future

Mutual toleration and institutional forbearance are procedural principles—they tell politicians how to behave, beyond the bounds of law, to make our institutions function.

We should worry when a politician 1) rejects, in words or action, the democratic rules of the game, 2) denies the legitimacy of opponents, 3) tolerates or encourages violence, or 4) indicates a willingness to curtail the civil liberties of opponents, including the media.