It would be understandable for denizens of Nashville, Houston, or Miami to be indifferent to the current fate of America’s troubled “blue cities.” New York, Chicago, San Francisco, and Detroit, for example, have become notorious for a toxic combination of street homelessness and crime, on top of pandemic population loss. All are governed by Democratic mayors and populated by Democratic majorities. The fact that these social ills can be linked directly to poor local governance, including bail “reform laws” that spring criminals, makes it even harder to feel these big cities’ pain. But indifference is far from the best response. In the vast, interconnected free trade zone known as the United States, a decline of what had been robust, job-producing cities affects the nation as a whole. And we all will, literally, pay the price. COVID ONLY ACCELERATED THE BLUE STATE EXODUS Throughout history, the cross-pollination of talent and ideas enabled by office life and proximity to others has sparked. That formula is threatened not only by the rise of the new home office but by the failure of cities (mainly those run by Democratic mayors) to provide basic public goods: safe streets, effective schools, well-maintained parks. What the economic historian Deirdre McCloskey has called the era of the “great enrichment” that has seen billions of people leave behind a life of poverty has, to a great extent, historically been based on the prosperity of...