Socialism is back in vogue. Wait for reality to set in.

Taxing the rich sounds good, until they move away.It has never been a better time in America to be a socialist. We aging Gen Xers who thought that socialism had been decisively refuted by the fall of the Berlin Wall have been refuted ourselves: Democratic socialists now run Seattle and New York City, and come January, probably D.C. too, where Janeese Lewis George won the Democratic primary that generally decides the district’s mayoral elections. It is a heady moment for the left, because socialism’s tainted brand has recovered from the vivid failures of the Soviet Union. Fully 66 percent of...