Now he’s after the Compleat Conspiracy, the one that explains it all: the rigged election, migrant Mexican rapists, the lying New York Times, thieving hedge funds, Obama-created ISIS, political correctness, women insufficiently attractive to grope, Chinese manufacturers, the Clinton Foundation. If it isn’t voting for Donald Trump and has recently crossed an international border, it’s a problem.

It did not escape notice that Mr. Trump’s remarks smacked of darker antipathies. A reporter for the New York Times suggested that the speech “echoed anti-Semitic themes.” The Daily Stormer, which bills itself as the premier publication of the alt-right, was less delicate, praising the speech for exposing the mass media as “the lying Jewish mouthpiece of international finance and plutocracy.”

But one needn’t accuse Mr. Trump of personal animus toward Jews (there’s no evidence of it) to point out that his candidacy is manna to every Jew-hater. Anti-Semitism isn’t just an ethnic or religious prejudice. It’s a way of thinking. If you incline to believe that the world is controlled by nefarious unseen forces, you might alight on any number of suspects: Freemasons, central bankers, the British foreign office. Somehow, the ultimate culprits usually wind up being Jews.