Has American democracy's long, ambitious run come to an end? Possibly yes. As William G. Howell and Terry M. Moe argue in this trenchant new analysis of modern politics, the United States faces a historic crisis that threatens our system of self-government-and if democracy is to be saved, the causes of the crisis must be understood and defused.

The most visible cause is Donald Trump, who has used his presidency to attack the nation's institutions and violate its democratic norms. Yet Trump is but a symptom of causes that run much deeper: social forces like globalization, automation, and immigration that for decades have generated economic harms and cultural anxieties that our government has been wholly ineffective at addressing. Millions of Americans have grown angry and disaffected, and populist appeals have found a receptive audience. These are the drivers of Trump's dangerous presidency. And after he leaves office, they will still be there for other populists to weaponize.

What can be done to safeguard American democracy? The disruptive forces of modernity cannot be stopped. The solution lies, instead, in having a government that can deal with them-which calls for aggressive new policies, but also for institutional reforms that enhance its capacity for effective action.

The path to progress is filled with political obstacles, including an increasingly populist, anti-government Republican Party. It is hard to be optimistic. But if the challenge is to be met, we need reforms of the presidency itself-reforms that harness the promise of presidential power for effective government, but firmly protect against the fear that it may be put to anti-democratic ends.