Kolko’s theory isn’t an outlier. There is a deep literature trying liberal residents to illiberal housing policies that create affordability crunches for the middle class. In 2010, UCLA economist Matthew Kahn published a study of California cities, which found that liberal metros issued fewer new housing permits. The correlation held over time: As California cities became more liberal, he said, they built fewer homes.

“All homeowners have an incentive to stop new housing,” Kahn told me, “because if developers build too many homes, prices fall, and housing is many families’ main asset. But in cities with many Democrats and Green Party members, environmental concerns might also be a factor. The movement might be too eager to preserve the past.”

The deeper you look, the more complex the relationship between blue cities and unaffordable housing becomes. In 2008, economist Albert Saiz used satellite-generated maps to show that the most regulated housing markets tend to have geographical constraints—that is, they are built along sloping mountains, in narrow peninsulas, and against nature’s least developable real estate: the ocean. (By comparison, many conservative cities, particularly in Texas, are surrounded by flatter land.) “Democratic, high-tax metropolitan areas … tend to constrain new development more,” Saiz concluded, and “historic areas seem to be more regulated.” He also found that cities with high home values tend to have more restrictive development policies.

One could attempt tying this together into a pat story—Rich liberals prefer to cluster near historic coastal communities with high home values, where they support high taxes, rent control, and a maze of housing regulations to protect both their investment and the region’s “character,” altogether discouraging new housing development that’s already naturally constrained by geography…—but even that interpretation elides the colorful local history that often shapes housing politics.