Similarly to the House, studying state delegations in the U.S. Senate allows us to see how delegations are behaving within a chamber before analyzing agenda crossover across chambers. By analyzing the legislative behavior of same state senators, coupled with the analysis of House delegations in Chapter 3, I continue to build toward the theory of agenda crossover that is addressed directly in Chapter 5. Studying same state senators is similar to the study of representatives in the House in that the senators represent a defined geographic area. However, state delegations in the Senate are different from their counterparts in the House because each senator also shares her constituents with the other senator from the state. This multimember structure allows for interesting and straightforward comparisons between the two senators within a state delegation, and is likely why state delegations in the Senate have been studied more recently than those in the House.

Based on the prominence scholars give to the electoral connection between members of Congress and their constituents, it seems intuitive to expect same state senators to appear similar in their legislative behavior. Yet the most recent scholarship on same-state senators suggests that they may actually have more to gain by distinguishing themselves from one other (Schiller 2000; Schiller and Cassidy 2011). In her book Partners and Rivals: Representation in U.S. Senate Delegations, Schiller compares the legislative behavior of senators from the same state and finds that these senators develop distinct legislative agendas and therefore are known to be experts in different issue areas. This runs somewhat counter to what scholars of representation might expect when studying senators from the same state. After all, the senators represent the same constituency, and therefore it is somewhat surprising that they do not focus on the same issues. However, Schiller finds that senators from the same state are incentivized to carve out a niche for themselves in Congress and become an expert in particular issue areas. On the one hand, this allows each senator to construct a legislative agenda that targets a subset of the state's policy interests, giving each senator as much leeway as possible to focus on issues he cares about. On the other hand, the number of potential issues relevant to the state is not limitless, and eventually the senators have to face the judgment of the voters every six years.