The “very small problem” Mellman has in mind is a trio of newly elected Democrats: Alexandria Ocasio-Cortez, Michigan’s Rashida Tlaib and Minnesota’s Ilhan Omar. They seem to have very few foreign policy views aside from a caricature of Israel as an occupying colonial force that sits up at night thinking of new ways to torment Palestinians.

Such ideas haven’t arisen from nowhere. They are the full flowering of decades of leftist propaganda and fashionable campus blatherskite. From such repellent acorns mighty trees grow, as we have seen in Europe. Britain’s Labour party did little to head off the virulent Israel hatred in its ranks, and it is now headed by an out-and-out anti-Semite.

In Britain, once-overwhelming Jewish support for Labour has cratered. A poll before the 2017 election found that only 13 percent of Jews supported Jeremy Corbyn’s Labour because of its horrid record on ­anti-Semitism.

That is why Mellman and his fellow Democrats are smart to be doing this now, before the conflict actually begins to bite. The problem is “very small” at this moment, but the party’s trend line to the left suggests it will grow in force absent some major intervention or ideological change of heart.