This week, Jews worldwide will celebrate the festival of Purim. It is a joyful holiday replete with lively rituals, especially the exuberant public reading of the Book of Esther.

The biblical text, set in ancient Persia during the reign of Ahasuerus (also known as Xerxes), recounts an attempt to exterminate the Jews. The plan is conceived by Haman, a fanatically antisemitic vizier who persuades the emperor that his Jewish subjects are disloyal. Ahasuerus signs a decree authorizing Haman “to destroy, massacre, and exterminate all the Jews, young and old, children and women … and to plunder their possessions.”

Fortunately the plot is thwarted, thanks to the efforts of the Jewish leader Mordecai and his cousin Esther, the Jewish heroine who becomes Ahasuerus’s queen. At the climactic moment, the emperor abruptly turns against Haman. In a rage, he orders him hanged and elevates Mordecai to be vizier in his place. As arbitrarily as he had condemned them, the emperor now champions the Jewish people. In the words of Esther 8:16, “The Jews had light and gladness and joy and honor.”

But for how long? The book ends with disaster averted and Mordecai and Esther enjoying royal favor. Yet Ahasuerus — as vainglorious, amoral, and mercurial as ever — remains firmly on the throne. What assurance do Persia’s Jews have that the capricious king who first endorsed genocide and then countermanded it isn’t going to reverse course again? One of the timeless lessons of Purim and the Book of Esther is that when society is ruled by depraved or unstable people, no one is safe — especially not vulnerable or vilified minorities like the Jews.

Again and again across the centuries, Jewish communities that believed themselves secure and welcome woke up to find themselves targeted by haters. Ten or 15 years ago it was still possible to believe that 21st-century America could never succumb to such antisemitic frenzy. But anyone with eyes to see knows better now.

In the wake of Oct. 7, 2023, Jew-hatred that was once confined to the fringes has spread toward the mainstream. Scores of college campuses have become hotbeds of anti-Jewish harassment and seething hostility to Israel. Vandals have attacked kosher restaurants and destroyed public menorahs. Crowds of protesters in Boston and elsewhere have called for “globalizing the intifada” — an exhortation to terrorize Jews wherever they live. Labor unions have grown overtly antisemitic; so have professional organizations like the American Psychological Association.

It is rare now to see a synagogue that doesn’t employ armed guards to keep worshipers safe. Jewish schools have had to sharply increase their already steep security outlays.

Antisemitic attitudes today run strongest among the young — on both sides of the political spectrum. Repeat: both sides.

For many years it was an article of faith among liberals, including liberal Jews, that antisemitism in America was primarily a right-wing phenomenon, found among white supremacists and neo-Nazis. More recently, the prevalence of left-wing antisemitism has been impossible to deny.

Republican leaders, to both their credit and their political advantage, have focused a spotlight on the eruption of antisemitic speech and demonstrations at progressive colleges. Last week the White House took the unprecedented step of revoking $400 million in federal funds to Columbia University over the school’s failure to protect Jewish students from harassment and bigotry.

Unfortunately, too many conservatives and Republicans are making the mistake that partisans on the left used to make and refusing to acknowledge that antisemitism on their side of the aisle remains a serious problem. During the 2024 campaign, Trump vowed to be the “best friend Jewish Americans have ever had in the White House.” More than a few Jews, especially among the Orthodox, believe it.

Yet the same administration that is targeting Columbia for tolerating antisemitism has just elevated a Pentagon spokesperson, Kingsley Wilson, who has a history of promoting antisemitic conspiracy theories. The same Trump who pledges to be a “best friend” to American Jews ostentatiously invited Jew-haters like Kanye West and the Holocaust denier Nick Fuentes to dinner at Mar-a-Lago. More broadly, antisemitism remains prevalent in sizable right-wing precincts, where influencers like Candace Owens demonize Jews with abandon and Joe Rogan provides a platform for extremists peddling anti-Jewish lies.

The Book of Esther opens with the description of an opulent party hosted by Ahasuerus — a party, the Talmudic sages taught, to which the cream of Persian Jewry was invited. The Jews of that era imagined that their position was secure, only to learn how quickly their stability could collapse once the air was poisoned with antisemitism. For Jews, vigilance is always imperative. From Haman to Hitler to Hamas and its supporters, the antisemitic derangement never disappears. As they do every year, Jews will gather this week to celebrate Purim. But the warmth of their joy will be tempered by the palpable chill of danger.