A Swing-State Theorem, with Evidence

We study the e↵ects of local partisanship in a model of electoral competition. Voters care about policy, but they also care about the identity of the party in power. These party preferences vary from person to person, but they are also correlated within each state or congressional district. As a result, most districts are biassed toward one party or the other (in popular parlance, most states are either ‘red’ or ‘blue’). We show that, under a large portion of the parameter space, electoral competition leads to maximization of the welfare of citizens of the ‘swing district,’ or ‘swing state,’ as the case may be: the one that is not biassed toward either party. The rest of the country is ignored. We show empirically that the US tari↵ structure is systematically biassed toward industries located in swing states, after controlling for other factors. Our best estimate is that the US political process treats a voter living in a non-swing state as being worth 70% as much as a voter in a swing state. This represents a policy bias orders of magnitude greater than the bias found in studies of protection for sale. ⇤University of Virginia and University of International Business and Economics (UIBE), Beijing, respectively. 1