Now that Sergei Lavrov has regurgitated a rumor popularized by an infamous Nazi to the effect that Hitler was part Jewish, the logical question is whether the Russian foreign minister will follow that Nazi’s late conversion and turn on his boss.

For now there is no indication that Mr. Lavrov plans to one day show remorse about blindly following Vladimir Putin. Yet, as Hans Frank’s example shows, even the most ardent supporter can turn on a charismatic leader after the dictator is gone. 

Frank was the Nazi governor of occupied Poland. Before being hanged at Nuremberg for his role in the mass murder of Jews, Frank became one of the first officials to make public the rumor, long-whispered in Berlin, that Hitler was partly Jewish. 

Although never substantiated, that rumor has been kept alive for decades, until it was repeated today by Mr. Lavrov. The Russian diplomat’s comment raised the ire of even those Israeli officials who had been advocating a balanced approach between Russia and Ukraine. 

Mr. Lavrov was answering an Italian journalist’s question about Moscow’s contention that it “denazifies” Ukraine, whose president is Jewish.

“If I remember correctly, yet I may be wrong, but Hitler also had Jewish blood, it meant absolutely nothing,” Mr. Lavrov said according to a translation provided by the Russian foreign ministry. “And we have long heard from the wise Jewish people who say that the most ardent anti-Semites are, as a rule of thumb, the Jews,” he added. 

Israel’s prime minister, Naftali Bennett, flew to Moscow shortly after Russia’s invasion of Ukraine. He met Messrs. Lavrov and Putin in an attempt to mediate an end to the war, which was also endorsed by President Zelensky. Unlike Foreign Minister Yair Lpaid, who had condemned Russian “war crimes,” Mr. Bennett had refrained from publicly criticizing Russia, perhaps in the hope that he could still be the mediator.

Today, however, Mr. Bennett addressed Mr. Lavrov’s comments head on: “Such lies are intended to accuse the Jews themselves of the most horrific crimes in history committed against them, thus freeing the responsibility from the oppressors of Israel,” the premier said. 

Even the Moldovan-born Israeli finance minister, Avigdor Liberman, who has kept ties with Moscow and remained mum since the beginning of the war, issued a strong denunciation of Mr. Lavrov’s reference for Hitler’s alleged Jewishness. 

Where does the idea arise that the worst enemy of the Jews in centuries was in fact a member of the tribe?

While imprisoned at Nuremberg, Hans Frank, an early convert to Nazi politics and once one of the fuhrer’s most enthusiastic followers, wrote an autobiography. In it he turned on his former boss, accusing Hitler of cultivating evil by employing “mass hypnosis” on the Germans and, like the devil, seducing men to follow him blindly. 

In his memoirs, Frank cited Hitler’s paternal grandmother, Maria Anna Schicklgruber, who worked as a cook for a well-to-do Jewish family, the Frankenbergers. The 42-year-old cook became pregnant out of wedlock, the identity of the father unknown. 

Frank cites an exchange of letters between the wealthy Jewish family and payments it made to Frauline Schicklgruber to raise her child, Alois. Were the payments made to prevent a lawsuit? Was the former cook impregnated by her employers’ 19-year-old son? If that is the case, then Alois, Hitler’s father, was half Jewish. 

Frank doesn’t make a clear determination about that possibility. He wrote that Alois’s real father could well have been Schicklgruber’s second cousin, Johann Georg Hiedler, a millworker who married her later on. The marriage legitimized Alois, who later changed his name to Hitler from Hiedler, and who sired the future fuhrer. 

During Hitler’s reign of terror the rumor of his alleged Jewishness was barely whispered. Frank later made it public, and it continued to reverberate as an intriguing pseudo-psychological explanation for the “Mein Kampf” writer’s obsession with Jews.

World War II and the Holocaust have for decades played a major role in Russia’s self-image. The Red Army’s sacrifices in the war are widely recited in Moscow. A Kremlin-backed annual UN resolution will next week commemorate the May 9 victory over the Nazis, and highlight Russia’s crucial part in it. 

Omitted from such ceremonies are inconveniences like the cooperation pact signed by the Soviet and Nazi foreign ministers, Vyacheslav Molotov and Joachim von Ribbentrop. Also overlooked are centuries of anti-Semitism in Russia, including the infamous “Elders of Zion” pamphlet, a fakery written in tsarist Russia and widely cited in Nazi literature, and Stalin’s own anti-Semitic trials in the 1950s. 

In a speech to the Knesset, Mr. Zelensky angered many Israelis by citing Ukraine’s help to Jews during the Holocaust, which in reality was quite rare and vastly overshadowed by Ukrainian cooperation in the Nazi extemination machine. 

Yet it was Mr. Lavrov who today was met with calls to end Holocaust comparisons to the Ukraine war. “Using the Holocaust of the Jewish people as a political tool must cease immediately,” Mr. Bennett said today. 

As he recites an unsubstantiated rumor spread by the likes of Frank, the question remains: Will Mr. Lavrov one day also try to defend himself and, similar to Frank, say he was merely “seduced” by Vladimir Putin?