Constituent diversity and congress: the case of NAFTA

An important finding of legislative research is that constituency variables are more important predictors of a legislator’s vote when constituent preferences are homogeneous, as opposed to when the various elements of the legislator’s constituency are pulling the legislator in opposing directions (Goff & Grier, Public Choice, 76, 5–20; Bailey & Brady, American Journal of Political Science, 42, 524–544). We examine these expectations on a highly salient vote, the 1993 senate vote on the North American Free Trade Agreement. While we find support for the view that constituency variables are more important in homogeneous than heterogeneous constituencies, we also find that by confining constituency variables to economic factors scholars overlook the importance of constituent ideology on legislator behavior in homogeneous constituencies.