When my best friend in Austin quips, “It’s great living in a blue city in a red state,” I’m often tempted to reply, “We really don’t know what it would be like to live in a red city in a red state – or even a red city in a blue state.”  Why?  Because they barely exist.  Zero cities with over one million people currently have Republican mayors.

From the standpoint of the textbook Median Voter Model, this is awfully puzzling.  Even if urbanites are extremely left-wing, you would expect urban Republicans to move sharply left to accommodate them.  Once they do so, the standard prediction is that Republicans will win half the time.  But plainly they don’t.

One possibility is that Republican politicians are too stubbornly ideological to moderate.  But the idea that virtually no one in the Republican Party is power-hungry enough to tell urban voters what they want to hear is deeply implausible.

The better explanation, as I’ve explained before, is that urban voters have party preferences as well as policy preferences.  They don’t just want left-wing policies; they want left-wing policies delivered by the Democrats.   Even if Republicans were offering exactly the same policies, urban voters would vote for the Democrats anyway.  Hence, one-party democracy, as they have in Singapore.

Once you buy this story, however, you just push the puzzle back a step.  Why exactly are big cities so uniformly inhabited by majorities who want left-wing policies delivered by the Democrats?

Economists will naturally gravitate to the functionalist story that left-wing policies are in the material self-interest of urban dwellers.  Yet this hard to believe.  How, for example, do classic left-wing policies toward the homeless serve the material self-interest of urbanites?  If anything, you would expect urbanites to favor draconian policies to “encourage” the homeless to go elsewhere.  Much the same goes for urban crime.

Even if this story were broadly true, however, it still wouldn’t explain the uniformity of left-wing cities.  You think there would be room for at least one mega-city that created a safe haven for rich urbanites who want to complacently enjoy their riches without having to deal with – or pay to remedy – any of the classic “urban problems.”  And it seems like a staunchly Republican city could easily deliver this package by offering little redistribution (or actively redistributing from poor-to-rich!) combined with punitive approaches to homelessness and crime.  Such policies don’t need to “work” in the sense of solving the social problem; they just need to work in the sense of exporting the social problem elsewhere.  Yet even if you broaden the sample to cities with just over a quarter million people, the vast majority of cities still lean left.

A popular alternative story emphasizes that cities are diverse and cosmopolitan, and Democrats are much more comfortable with diversity and cosmopolitanism.  But this answer dodges multiple questions, starting with: “Why can’t urban Republicans just get comfortable with diversity and cosmopolitanism, then win half the time?”  Plus: “Why isn’t there a single city that isn’t diverse or cosmopolitan?”  One can easily imagine a Patriot City of straight, white Trump supporters.

A better story, in my view, is that (a) cities provide anonymity, (b) anonymity reduces the cost of violating traditional norms, and (c) Republicans value traditional norms more.  True, you still need voters to have strong party preferences for this story to work.  Main problem: This story implies that when left-wing norms become tradition, the socially conservative minority will move to cities to escape.   Hard to believe, but testable!  You could even tweak the preceding account into a habit formation story: when you lower the cost of violating traditional norms, people start violating them.  Eventually, they get used to violating them, which eventually makes them disfavor traditional norms.

Main doubt: It is not entirely clear that norm violation is easier in cities.  Think about mask-wearing norms.  While you are more anonymous in cities, you are also surrounded by a much larger number of self-appointed norm-enforcers.

Better stories?  Try to ponder both the Median Voter Model and the Tiebout Model before you answer.