Abstract
Scholarly work has missed the key reason for the extraordinary levels of political polarization and poor governance in American politics in recent years. Contrary to the appearance that strong party leaders dictate member behavior, we argue that weak party discipline produces polarizing rhetoric in lieu of actionable policy proposals. We attribute this weak discipline to the rising number of safe House districts that play into the hands of extreme primary electorates. First, we provide comprehensive historical evidence of the rise of safe seats in U.S. House districts and show that this trend coincides with the greater divergence of legislators’ preferences not just between but also within parties. Second, we demonstrate that representatives from safer districts-and especially those from the GOP-have more ideologically extreme and divergent preferences across multiple alternative measures. We then use redistricting as a plausible source of exogenous variation in electoral competition and corroborate that seat safety causes ideological extremism. Finally, we explore the potential mechanisms behind this relationship, showing that the more-extreme ideological tendencies in safer seats are likely present due to a combination of more extreme electorates, primary challengers, and donor influence there, which can all undermine legislators’ willingness to support their party agendas.