It seems implausible that long-lived institutions, like political parties in the United States, would continue if they have no function. Yet Keith Krehbiel (1993; 1998; 1999) has posed the provocative argument that political parties are excess baggage when explaining decision making in the U.S. Congress. Krehbiel has argued, theoretically, empirically, and eloquently, that political parties are little more than costume jewelry on the dowager of theory -- flashy and pretty, but contributing little to the basic underlying material. As such, Krehbiel has proposed that scholars locate the value of political parties, both theoretically and empirically. By doing so, he has forced scholars who have taken political parties as fundamental political primitives to step back and clarify exactly what it is that parties do.
The response to Krehbiel has been plentiful. An enormous amount of empirical work has been brought to bear on his critique, trying to show that party has an effect independent of pure preference. Some theoretical work has challenged the model by more explicitly incorporating parties (Rohde, 1991; Aldrich, 1994). The theoretical work is interesting, but finds it difficult to accommodate complex relationships between many actors. The empirical work, undertaken by a variety of scholars, yields mixed results. Nonetheless parties are an observable phenomenon and they persist. It has been observed that partisan effects wax and wane over time (see Cooper, Brady and Hurley, 1979; Patterson and Caldeira, 1988; Hurley and Wilson, 1989; Cooper and Young, 1999). The difficulty with pinpointing the effect of party has driven scholars to accept Krehbiel's challenge and to address it in a serious manner.
This research starts with Krehbiel's point that traditional measures of party voting and party unity do not tap a pure partisan effect. The first section elaborates some of the issues and concerns about partisanship and "preferenceship." The second section develops Krehbiel's critique of the party literature and then explores an alternative way of thinking about roll call votes and their analysis. The third section develops a bootstrapping technique by which to compare outcomes under roll call votes. The fourth and fifth sections develop hypotheses and analyze these data. The conclusion returns to the main point, asking whether the evidence developed here is an expression of partisanship removed from pure preference.