Cause and Effect in Political Polarization: A Dynamic Analysis

Political polarization is an important and enduring puzzle. Complicating attempts at explanation is that polarization is not a single thing. It is both a description of the current state of politics today and a dynamic path that has rippled across the political domain over multiple decades. In this paper we provide a simple model that is consistent with both the current state of polarization in the U.S. and the process that got it to where it is today. Our model provides an explanation for why polarization appears incrementally and why it was elites who polarized first and more dramatically whereas mass polarization came later and has been less pronounced. The building block for our model is voter behavior. We take an ostensibly unrelated finding about how voters form their preferences and incorporate it into a dynamic model of elections. On its own this change does not lead to polarization. Our core insight is that this change, when combined with the response of strategic candidates, creates a feedback loop that is able to replicate many features of the data. We explore the implications of the model for other aspects of politics and trace out what it predicts for the future course of polarization