Sequential Choices and Partisan Transitions in U.S. Senate Delegations: 1972-1988

A recent increase in the number of states sending mixed delegations to the U.S. Senate, i.e., having one senator of each political party, has led scholars to ask why essentially stable electorates produce different partisan outcomes. We contend that the existing arguments do not, and cannot, adequately explain this phenomenon. The failure of these earlier attempts is the direct result of a misinterpretation of the choices faced by voters in sequential elections. The existence of mixed Senate delegations is not all that extraordinary in an era of candidate-centered, rather than party-centered, campaigns. In short, sequential, binary decisions are not equivalent, and mixed delegations are perfectly consistent with general expectations of voting behavior and electoral politics. A model consisting of election-specific variables is used to predict transitions to and from mixed delegations, and to directly test, and reject, the primary existing explanation.