Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)



First Advisor

William J. Moore


Based on the economic theory of regulation, our model portrays U.S. senators as utility-maximizing agents and the American Medical Association (AMA) as a rational contributor. We use contributions from the AMA's political arm, the American Political Action Committee (AMPAC), and roll call votes in the U.S. Senate from 1979-1992 to test for AMPAC contributions effects, to test the hypothesis that the AMA "rewards" senators for their voting behavior, and to determine the role of issue specificity. We use pooled, cross-sectional data in a simultaneous Probit-Tobit-Generalized Least Squares framework and extend the traditional analyses by examining alternative timing specifications, election year and nonelection year samples, and Senate committee members and nonmembers. We obtain estimates of the standard errors by using bootstrap procedures which do not rely on asymptotic assumptions. We find no strong evidence that the AMA is successful in capturing legislation nor any evidence that the AMA rewards (or punishes) voting behavior. There is weak evidence that senators respond to future AMA contributions when voting on bills especially important to the AMA. We also find weak evidence that (future) key votes explain AMA contributions. Tests show that the underlying process generating AMA contributions is different for election years and nonelection years, and for Senate committee members and nonmembers.