What is clear is that these strains of anti-Semitism — from the right, from the left and from radical Muslims — have morphed into a resurgence of a blight that should have been eradicated long ago, and that is causing serious anxiety among Europe’s Jews.

A CNN poll last November on the state of anti-Semitism in Europe found that a third of respondents said they knew little or nothing about the Holocaust. Nearly a quarter said Jews had too much influence in conflict and wars; more than a quarter said they believed that Jews had too much influence in business and finance. A 2015 survey by the Anti-Defamation League found that 51 percent of Germans believed it was “probably true” that “Jews still talk too much about what happened to them in the Holocaust.” These are the stereotypes that make anti-Semitism an especially pernicious form of bigotry, a grand conspiracy theory in which Jews spread evil in their countries through some illusory subterfuge, whether controlling capital, or the media, or whatever.

All this is not news to European Jews, who for some time have been feeling less and less safe and welcome in their home countries. After polling more than 16,000 Jews in 12 European countries at the end of last year, the European Union’s Agency for Fundamental Rights concluded that anti-Semitic hate speech, harassment and fear of being recognized as Jews were becoming the new normal. Eighty-five percent of the respondents thought anti-Semitism was the biggest social and political problem in their countries; almost a third said they avoided Jewish events or sites because of safety concerns. More than a third said they had considered emigrating in the five years preceding the survey.