Part I. Why Might Polarization Harm Democracy? Theory and Comparison; 1. How Democracies Endure: The Challenges of Polarization and Resilience Robert C. Lieberman, Suzanne Mettler, and Kenneth M. Roberts; 2. Polarization and the Durability of Madisonian Checks and Balances: A Developmental Analysis Paul Pierson and Eric Schickler; 3. Pernicious Polarization and Democratic Resilience: Analyzing the United States in Comparative Perspective Jennifer McCoy and Murat Somer; Part II. Political Institutions in Polarized Times; 4. Cross-Cutting Cleavages, Political Institutions, and Democratic Resilience in the US Frances E. Lee; 5. Unilateralism Unleashed? Polarization and the Politics of Executive Action Douglas L. Kriner; 6. Court-Packing and Democratic Erosion Thomas M. Keck; Part III. Social Polarization and Partisanship; 7. The Social Roots, Risks, and Rewards of Mass Polarization Lilliana Mason and Nathan P. Kalmoe; 8. The Great White Hope: Threat and Racial Resilience in the Age of Trump Christopher Sebastian Parker and Matt A. Barreto; 9. The Religious Sort: The Causes and Consequences of the Religiosity Gap in America Michele F. Margolis; 10. Weaponized Group Identities and the Health of Democracy: Why the National Rifle Association is Good at Democracy but Bad for It Matthew J. Lacombe; Part IV. Vicious Circles? The Relationship Between Polarized Behavior and Institutions; 11. Polarization, the Administrative State, and Executive-Centered Partisanship Desmond King and Sidney Milkis; 12. Laboratories of What? American Federalism and the Politics of Democratic Subversion Philip Rocco; 13. Conservative Extra-Party Coalitions and Statehouse Democracy Alexander Hertel-Fernandez; Part V. Can Political Action Save Democracy in Polarized Times? 14. Elections, Polarization, and Democratic Resilience David A. Bateman; 15. Citizen Mobilization and Partisan Polarizations from the Tea Party to the Anti-Trump Resistance Theda Skocpol, Caroline Tervo, and Kirsten Walters.