In the last few weeks, the unimaginable has become distinctly possible: that one of the two main political parties in the United States, the world’s hyper-power, the great democratic beacon of the modern age, will succumb to the wiles of a demagogue taking his cues from a Fascist propaganda playbook.

That, come November, American voters will face a choice that could result in a race-and-religion-baiting thug occupying the White House.

It is one of the most fateful moments in America’s long political history.

Donald Trump has run by far the ugliest, and crudest, political campaign for high office since the segregationist candidacy of George Wallace in 1968.

He has tapped into a deep vein of fear – about terrorism, about immigration, about downward mobility, about cultural and sexual mores changing rapidly and profoundly – and a groundswell of authoritarian sentiment in parts of the country to build up a coalition based largely around the fueling of hate.

When Trump is criticized, his supporters whip up a storm of vitriol in cyberspace. Essayists like Bethany Mandel, who has been tracking Trump’s xenophobic rhetoric since the summer, have been ruthlessly attacked, often with deeply anti-Semitic language.

“Trump’s round-them-up-and-deport-them mindset, along with his aspersions cast on Mexican immigrants, is disturbingly similar to the slurs historically hurled at Jews and other newcomers. Jews were labeled con artists and thieves; Mexicans are, according to Trump, “rapists” and violent criminals,” Mandel wrote in the Forward in August.

She has been labeled a “slimy Jewess,” and has been told she deserves the oven. Mandel just announced she was buying a gun for protection in the wake of the abuse that she fears might become physical threats

Nation of Islam leader Louis Farrakhan recently praised Trump for refusing to accept money from Jewish donors. The Ku Klux Klan has wholeheartedly endorsed the man. The neo-Nazi Daily Sturmer website has enthused about him.

When I traveled to Nevada last week to interview Trump supporters at the caucus there, time and again those supporters told me they thought American Muslims should be deported or should be killed. They were talking about ALL Muslims. Period. Some of those same people made a point of asking me, when they heard my name, if I was Jewish. The undertone of menace was unmistakable.

These are men and women who have a two dimensional vision of America: that of a white and a Christian nation. They have no truck with pluralism; no time for diversity. It is a narrow, bigoted worldview, and they feel, finally, that in Trump their moment is at hand.

Trump’s post-Super Tuesday speech,in which he shamelessly claimed to be a unifying,inclusive, candidate, would have been laughable had the damage he has already caused not been so deep.

Trump has called for the barring of Muslims from entering the country; for the registration of Muslims already living in the country; for the building of a “beautiful” wall between the U.S. and Mexico; for the wholesale and immediate deportation of more than 11 million undocumented residents.

He has, repeatedly, said that he wants to smash the faces of protestors. He has advocated the summary execution of terrorism suspects – and their families. And he has ridiculed the disabled, the poor, and pretty much every other non-white and non-wealthy group of people.

He has failed to adequately denounce his support from the KKK, re-tweeted quotes attributed to Mussolini and a cluster of other white supremacist groups, and has been cheered on by French fascist Jean-Marie LePen – who once declared the Holocaust to be a footnote of history. Like the LePen family, he is piggy-backing on feelings of white alienation and anger at Muslim immigrants to create a mass movement.

He now has a chance to best even their best electoral results so far if he manages to take over the party that controls the U.S. Congress and 28 of the fifty governorships.

Trump has gone from one blustery insult to the next and each step of the way he has, like the Fascist politicians of earlier decades, built up his support by promising national salvation and by advocating an iron fist against ethnic and political enemies.

It is no coincidence that the country is seeing a spasm of race-related hate-crimes, including the execution-style murder of three Muslim students in Indiana last week.

It is no coincidence that the KKK rallied in southern California last week.

Trump is unleashing beasts, and, even if he occasionally tones down the rhetoric and comes off as moderate – as he went out of his way to do in his victory speech Tuesday night – he has created by far the most noxious and dangerous political coalition in modern American history.

I think often, these days, of the famous lines by Martin Niemoller, and how they might be updated to reflect the multi-ethnic pastiche of modern America:

“First they came for the Muslims/And I did not speak out/Because I was not a Muslim.

Then they came for the Mexicans/And I did not speak out/Because I was not a Mexican.

Then they came for the feminists and the gays/And I did not speak out/Because I was not feminist or gay

Then they came for the blacks/And I did not speak out/Because I was not black.

Then they came for me/And there was no one left/To speak out for me.”

I think of the incredulity that cultured, decent Weimar Germans had when Hitler came on the political scene. I think of how they treated him as a coarse joke, as something to laugh at rather than to be terrified by. I think of those German workers, in the beer halls, talking about how Hitler would make Germany great again. I think of those same workers, listening, glassy-eyed, as Hitler explained how the Jews had stabbed their glorious fatherland in the back. I think of how they trooped to the polls in 1932, longing for national salvation, enough of them turning out for the Nazis that Hitler’s rise to power became all-but-impossible to stop.

I think of how quickly that great and cultured country slid into barbarism, and of how completely a demagogue managed to capture and to mold all of the institutions of state.

Trump has hypnotized many millions of Americans, and he has read the mood of an angry, disempowered, scared, and frustrated electorate extraordinarily well. He plays one group against another with seeming ease. He’s good enough at this that he could even try to appeal to Jewish voters in Florida by ginning up his anti-Muslim language in time for the Florida primary later this month. It would be catastrophic if it worked.

There is no more urgent task facing the American political system – and the international system as a whole, which is so intimately interconnected with the United States – than to find a way to break this demagogue before he breaks the political system of the world’s pre-eminent democracy.