Will we stop Trump before it’s too late? Fascism poses a more serious threat now than at any time since the end of World War II.

On April 28, 1945 — 73 years ago — Italians hung the corpse of their former dictator Benito Mussolini upside down next to a gas station in Milan. Two days later, Adolf Hitler committed suicide in his bunker beneath the streets of war-ravaged Berlin. Fascism, it appeared, was dead.

To guard against a recurrence, the survivors of war and the Holocaust joined forces to create the United Nations, forge global financial institutions and — through the Universal Declaration of Human Rights — strengthen the rule of law. In 1989, the Berlin Wall came down and the honor roll of elected governments swelled not only in Central Europe, but also Latin America, Africa and Asia. Almost everywhere, it seemed, dictators were out and democrats were in. Freedom was ascendant.

Today, we are in a new era, testing whether the democratic banner can remain aloft amid terrorism, sectarian conflicts, vulnerable borders, rogue social media and the cynical schemes of ambitious men. The answer is not self-evident. We may be encouraged that most people in most countries still want to live freely and in peace, but there is no ignoring the storm clouds that have gathered. In fact, fascism — and the tendencies that lead toward fascism — pose a more serious threat now than at any time since the end of World War II.

Warning signs include the relentless grab for more authority by governing parties in Hungary, the Philippines, Poland and Turkey — all United States allies. The raw anger that feeds fascism is evident across the Atlantic in the growth of nativist movements opposed to the idea of a united Europe.

Around the Mediterranean, the once bright promise of the Arab Spring has been betrayed by autocratic leaders, such as Abdel Fattah el-sisi of Egypt (also just reelected), who use security to justify the jailing of reporters and political opponents.

Thanks to allies in Moscow and Tehran, the tyrant Bashar al-assad retains his stranglehold over much of Syria. In Africa, the presidents who serve longest are often the most corrupt, multiplying the harm they inflict with each passing year. Meanwhile, the possibility that fascism will be accorded a fresh chance to strut around the world stage is enhanced by the volatile presidency of Donald Trump.

If freedom is to prevail over the many challenges to it, American leadership is urgently required. This was among the indelible lessons of the 20th century. But by what he has said, done and failed to do, Mr. Trump has steadily diminished America’s positive clout in global councils.

Instead of mobilizing international coalitions to take on world problems, he touts the doctrine of “every nation for itself” and has led America into isolated positions on trade, climate change and Middle East peace. Instead of engaging in creative diplomacy, he has insulted United States neighbors and allies, walked away from key international agreements, mocked multilateral organizations and stripped the State Department of its resources and role. Instead of standing up for the values of a free society, Mr. Trump, with his oft-vented scorn for democracy’s building blocks, has strengthened the hands of dictators. No longer need they fear United States criticism regarding human rights or civil liberties. On the contrary, they can and do point to Mr. Trump’s own words to justify their repressive actions.

At one time or another, Mr. Trump has attacked the judiciary, ridiculed the media, defended torture, condoned police brutality, urged supporters to rough up hecklers and — jokingly or not — equated mere policy disagreements with treason. He tried to undermine faith in America’s electoral process through a bogus advisory commission on voter integrity. He routinely vilifies federal law enforcement institutions. He libels immigrants and the countries from which they come. His words are so often at odds with the truth that they can appear ignorant, yet are in fact calculated to exacerbate religious, social and racial divisions. Overseas, rather than stand up to bullies, Mr. Trump appears to like bullies, and they are delighted to have him represent the American brand. If one were to draft a script chronicling fascism’s resurrection, the abdication of America’s moral leadership would make a credible first scene.

Equally alarming is the chance that Mr. Trump will set in motion events that neither he nor anyone else can control. His policy toward North Korea changes by the day and might quickly return to saber-rattling should Pyongyang prove stubborn before or during talks. His threat to withdraw from the 2015 Iran nuclear agreement could unravel a pact that has made the world safer and could undermine America’s reputation for trustworthiness at a critical moment. His support of protectionist tariffs invites retaliation from major trading partners — creating unnecessary conflicts and putting at risk millions of export-dependent jobs. The recent purge of his national security team raises new questions about the quality of advice he will receive. John Bolton starts work in the White House on Monday.

What is to be done? First, defend the truth. A free press, for example, is not the enemy of the American people; it is the protector of the American people. Second, we must reinforce the principle that no one, not even the president, is above the law. Third, we should each do our part to energize the democratic process by registering new voters, listening respectfully to those with whom we disagree, knocking on doors for favored candidates, and ignoring the cynical counsel: “There’s nothing to be done.”

I’m 80 years old, but I can still be inspired when I see young people coming together to demand the right to study without having to wear a flak jacket.

We should also reflect on the definition of greatness. Can a nation merit that label by aligning itself with dictators and autocrats, ignoring human rights, declaring open season on the environment, and disdaining the use of diplomacy at a time when virtually every serious problem requires international cooperation?

To me, greatness goes a little deeper than how much marble we put in our hotel lobbies and whether we have a Soviet-style military parade. America at its best is a place where people from a multitude of backgrounds work together to safeguard the rights and enrich the lives of all. That’s the example we have always aspired to set and the model people around the world hunger to see. And no politician, not even one in the Oval Office, should be allowed to tarnish that dream.

Madeleine Albright, the author of “Fascism: A Warning,” served as United States secretary of state from 1997 to 2001.

The above article was first published in The New York Times.