There is general agreement that ideological polarization in the U. S. House and Senate has increased over the last generation, and that this change has contributed to congressional deadlock in areas such as deficit reduction. However, the mechanism that links polarization to deadlock is unclear - why does polarization make agreements harder to achieve?
Using new game-theoretic technology, we characterize the impact of polarization on congressional outcomes over the last 30 years. We identify a link between polarization and deadlock that arises because of the bicameral organization of the U. S. Congress. When disagreements between Republicans and Democrats become sufficiently large and organized along a single ideological dimension, and when divided government exists (each party controls one chamber of Congress), any proposal that is enactable in one chamber cannot be enacted in the other. That is, under these conditions, deadlock arises because of disagreements between the chambers, rather than within one or the other.