Originally published in Times of Israel

Ask British Jews what advice they would offer to American Jews, based on their experience fighting Corbynism, and the answer is unequivocal: Don’t wait until it’s almost too late to fight for your political home. Don’t pretend it can’t happen to you.

They mean: Pay attention to how quickly a mainstream party with a long pro-Israel tradition and deep roots in the Jewish community can be transformed into a home for enemies of the Jewish people.

Bernie Sanders is not Jeremy Corbyn, and the Democratic Party is not Labour. Sanders has repeatedly affirmed his support for Israel’s right to exist (though he is far more equivocal about its right to defend that right). We all know about his time on a kibbutz. And the Democratic Party has an overwhelming majority of pro-Israel legislators.

But more than any other leading politician, Sanders is responsible for mainstreaming the Corbynist wing of the Democratic Party. The party’s anti-Zionists, like Linda Sarsour, have gathered around Sanders. And Sanders himself supported Corbyn — ignoring the fears of British Jews, who overwhelmingly saw Corbyn as an anti-Semite.

Corbyn has shown us how quickly the politics of the fringe can become mainstream. Under President Sanders, those still-renegade voices within the Democratic Party would have intimate access to the White House.

In his first months in office, President Trump emboldened the far-right fringe. President Sanders would do the same with the far left.

Sanders recently spoke movingly about the impact of the Holocaust on his sensitivity to racism and injustice. And yes, he hates anti-Semitism — right-wing anti-Semitism. The anti-Semitism in his own camp seems to leave him indifferent.

Bernie is that Jew who has taken his people’s suffering and offered it entirely outward, in the service of other causes. After his stay on a kibbutz, Bernie the Jew seems to have gone AWOL. Did he stand with Israel in 1967? 1973? In 1975, when the UN labeled Zionism racism? Did his Holocaust-driven pain lead him to active involvement in the movement to free Soviet Jewry — the most important American Jewish political response to the Holocaust?

And then there’s the video clip of Sanders, taken during his Soviet honeymoon in 1988, sitting bare chested in a sauna and toasting Soviet officials. That astonishing scene portrays a Jew indifferent to his people’s torment.

Those on the right who try to portray him as a “communist” only confuse the essential debate over Bernie with foolish accusations. The reality is problematic enough: Bernie is a European-style socialist, which means he is a democrat with a soft spot for anti-democratic revolutionaries.

Bernie is also a uniquely American irony: The first serious Jewish candidate for president turns out to be a man-child who never left the ‘60s, who delights in the rhetoric of “revolution,” and recklessly threatens to undo the American economy and, with it, American power. (Asked in a recent interview how many trillions his programs will cost, he effectively shrugged and said, Who knows? No one knows! How should I know?)

A Trump-Sanders contest would be a political nightmare for American Jewry. It would undermine whatever minimal consensus still holds the American Jewish community together. In that toxic atmosphere, pro-Sanders and pro-Trump Jews would each accuse the other of betraying Jewish values. And both would be right.

Those Jews who passionately support Trump need to ask themselves whether their man is at least partly responsible for the threat of a Sanders presidency. The politics of rage, from whatever source, are never good for Jews. Inevitably, the ecstasy of the crowd blurs political lines. When all norms shatter, anything becomes possible.

A Trump-Sanders race would cut to the heart of American Jewish identity. It would reduce the two essential elements of contemporary Jewish identity — particularism and universalism — to farce. In that race, Trump would be the “Jewish particularist,” chastising universal-minded Jews for betraying Israel. And Sanders would be the “tikkun olamist,” drawing on Jewish history only to justify his dismissal of explicitly Jewish concerns.

Bernie Sanders is not an enemy of the Jewish people. He simply doesn’t care enough about Jewish concerns to be considered a friend.

President Sanders would be taking office at a time when the stakes could not possibly be higher for Israel. The current low-key Israeli-Iranian war could transform at any moment into a full-scale, multi-front regional conflict. The IDF has repeatedly warned that, in the next phase of this ongoing war, tens of thousands of missiles and rockets will fall on Israeli cities. Israel, according to the IDF, will respond with a massive invasion of southern Lebanon and the destruction of Lebanon’s infrastructure. The Israeli counter-attack could widen to include targets in Iran itself.

In that entirely realistic scenario, whose side would President Bernie be on?