Investment in publicly subsidized social housing units—designed to ensure long-term access to dwellings for households with low and moderate incomes—is a key strategy cities around the world leverage to increase housing affordability. But the availability of such affordable units varies tremendously between cities, even within the same country. To what degree is this variation the product of local politics expressed through voter or policymaker preferences?

To answer this question, I examine the inclusion of social housing in major development projects planned in hundreds of municipalities across the Paris, France metropolitan region. Through a series of multiple regression analyses, I demonstrate that cities with left-wing councils plan for an average of 7 to 11 percentage-point higher social-housing shares in new projects, compared to cities with right-wing or centrist councils, and after controlling for the ideologies of local residents, preexisting levels of social housing, and community demographic characteristics. Though the political preferences of voters are closely associated with city-level social housing shares, elected officials’ partisanship provides a key explanation for variations in the provision of social housing in newly approved projects. I reaffirm these findings by using a series of regression discontinuity tests to examine differences between communities with close elections. These results show the importance of the partisan affiliations of local leaders in making urban planning choices for their communities.