The more serious Democratic Party problem with Ms. Ocasio-Cortez and Ms. Omar is not that their great talent seems to be for political manipulation, or that they constantly set fires, portray the universe as consisting of angels and demons, and put people off with their arrogance while exciting them with their ferocity—though all these things are true.

It is that in doing these dramatic things, and amplifying them through their impressive social-media skills, or compulsions, they have fully broken through and made their mark. In their fame and celebrity they altered the face and feel of the party into something that appears more radical, more hissing and accusatory, more hard-left.

Ms. Ocasio-Cortez’s success last June scared fellow Democrats across the country into thinking she is the future, that they must get aboard and get with her program, which many of the party’s presidential nominees have. She has very effectively changed the ideological shape of the Democratic Party with her de facto open-borders policy and other extremisms.

Mature liberals and moderates know this will come back to bite them.