In Malaysia, Prime Minister Mahathir Mohamad used a politically loyal police force and a packed judiciary to investigate, arrest, and imprison his leading rival, Anwar Ibrahim, on sodomy charges in the late 1990s.

President Trump demonstrated striking hostility toward the referees – law enforcement, intelligence, ethics agencies, and the courts.

Two basic norms have preserved America’s checks and balances in ways we have come to take for granted: mutual toleration, or the understanding that competing parties accept one another as legitimate rivals, and forbearance, or the idea that politicians should exercise restraint in deploying their institutional prerogatives.

That brings us to a final factor shaping President Trump’s ability to damage our democracy: crisis. Major security crises – wars or large-scale terrorist attacks – are political game changers. Almost invariably, they increase support for the government. Citizens become more likely to tolerate, and even endorse, authoritarian measures when they fear for their security.

Those who denounce government abuse may be dismissed as exaggerating or crying wolf. Democracy’s erosion is, for many, almost imperceptible.

Demagogues attack their critics in harsh and provocative terms – as enemies, as subversives, and even as terrorists.

Some of history’s most tragic democratic breakdowns were preceded by the degrading of basic norms.

It was the Civil Rights Act, which Democratic president Lyndon Johnson embraced and 1964 Republican presidential candidate Barry Goldwater opposed, that would define the Democrats as the party of civil rights and Republicans as the party of racial status quo.

These two norms undergirded American democracy for most of the twentieth century. Leaders of the two major parties accepted one another as legitimate and resisted the temptation to use their temporary control of institutions to maximum partisan advantage.

The second category in our litmus test is the denial of the legitimacy of one’s opponents. Authoritarian politicians cast their rivals as criminal, subversive, unpatriotic, or a threat to national security or the existing way of life.