The Institutional Consequences of Congressional Polarization

Polarization, defined as the ideological distance between the Democrat and Republican parties in Congress, has increased dramatically in Congress since the 1970s. Research on polarization in the U.S. Congress primarily focuses on the sources of this increase. Relatively little work has been done on the consequences of polarization for Congress? relationship with the president and the passage of legislation. This dissertation corrects this omission by examining the influence of polarization on several key aspects of the legislative process. It examines the impact of polarization on the interaction between Congress and the president, including the president?s strategy in supporting or opposing legislation and the success the president has on bills when he takes a position. It also examines the effect polarization has on the overall passage of legislation. An empirical examination was undertaken using significant bills in Congress over a sixty year time period (1947-2006). The results indicate that the effects of polarization on the legislative process are contingent upon the presence of divided government, defined as times when the president and a majority of members of Congress are from different parties, and the chamber of Congress under examination. As polarization increases, the president is more likely to support legislation and be successful when his party controls Congress, but he opposes more legislation and is less successful as polarization increases under divided government. Legislative gridlock, the inability of Congress to pass important or innovative legislation, tends to decrease in both the House and Senate as polarization increases under unified government. However, as polarization increases under divided government the overall passage of bills into law decreases. The dissertation also offers an improved method for modeling the impact of divided government on gridlock. Prior studies model divided government without regard for whether the president takes a position on a given bill. This study shows that when the president takes a position on a bill under divided government the probability it passes decreases, but the probability of passage increases when the president does not take a position. This finding implies that previous research may underestimate the true effects of divided government on gridlock.