JOEL KOTKIN: The regression of America’s big progressive cities.

If there’s anything productive to come from his recent Twitter storm, President Trump’s recent crude attacks on Baltimore Congressman Elijah Cummings have succeeded in bring necessary attention to the increasingly tragic state of our cities. Baltimore’s continued woes, after numerous attempts to position itself as a “comeback city,” illustrates all too poignantly the deep-seated decay in many of our great urban areas.

Baltimore represents an extreme case, but sadly it is not alone. Last year our three largest urban centers — New York, Los Angeles and Chicago — lost people while millennial migration accelerated both to the suburbs and smaller, generally less dense cities. These demographic trends, as well as growing blight, poor schools, decaying infrastructure and, worst of all, expanding homelessness are not merely the result of “racism” or Donald Trump, but have all been exacerbated by policy agendas that are turning many great cities into loony towns.

Take tech rich San Francisco, where decades of tolerance for even extreme deviant behavior has helped create a city with more drug addicts than high school students, and so much feces on the street that one website has created a “poop map.” In Southern California’s far more proletarian city of Los Angeles, we have a downtown filled with overbuilt, overpriced apartments and is, like Baltimore, being overrun with rats. A UN official last year compared conditions on the city’s Skid Row to those of Syrian refugee camps.

One would think such nasty problems would spark something of a political rebellion, as seen in previous decades with the rise of successful, pragmatic mayors — Bob Lanier and Bill White in Houston, Rudy Giuliani and Michael Bloomberg in New York, and Richard Riordan in Los Angeles. But so far, at least, many of today’s big city mayors seem more interested in bolstering their “resistance” bona fides than governing effectively. . . .

The new urban politics threatens the future of family neighborhoods, local entrepreneurial ventures as well as an apolitical, exuberant diversity. Immigrants and aspiring minorities want good schools, safe streets and less onerous regulation. Resolutions on sanctuary cities, condemnations of Trump tweets, social justice demands and boasts about combating climate change do little to improve tangibly reality that cities like Baltimore or even superstars like San Francisco, Washington, and New York.

Only when grassroots people and concerned businesses decide to challenge the urban status quo and the virtue-signaling political class can decay and the relentless bifurcation of our cities be reversed.

The problem is that our cities, like many of our institutions, are run by people who care more about their standing with their peers than about the state of the institutions they’re in charge of.