The Founders created a representative republic rather than a direct democracy, designed to slow down deliberation so that majorities could rule based on reason rather than passion. But in the age of Facebook and Twitter, new social media technologies have unleashed populist passions and accelerated public discourse to warp speed, creating the very mobs, demagogues, echo chambers, and factions that Madison and Hamilton feared. Is the American idea in crisis, and if so, what can we do about it?