Credibility and Policy Convergence: Evidence from U.S. House Roll Call Voting Records

Traditional models of politician behavior predict complete or partial policy convergence, whereby electoral competition compels partisan politicians to choose positions more moderate than their most-preferred policies. Alternatively, if politicians cannot overcome the inability to make binding pre-commitments to policies, the expected result is complete policy divergence. By exploiting a regression discontinuity (RD) design inherent in the Congressional electoral system, this paper empirically tests the strong predictions of the complete divergence hypothesis against the alternative of partial convergence within the context of Representatives' roll call voting behavior in the U.S. House (1946-1994). The RD design implies that which party wins a district seat is quasi-randomly assigned among elections that turn out to be 'close'. We use this variation to examine if Representatives' roll call voting patterns do not respond to large exogenous changes in the probability of winning the election, the strong prediction of complete policy divergence. The evidence is more consistent with full divergence and less consistent with partial convergence, suggestive that the difficulty of establishing credible commitments to policies is an important real-world phenomenon.