In researching this book, Sarah Treul functioned as something of an archaeologist. As her literature review demonstrates, previous research into the role of state delegations in the U.S. House was conducted not simply before Treul joined the profession but before she was born. Scholars working in the 1960s and 1970s explored the degree to which delegations united to promote their state’s interests by bloc voting, sharing information, and insuring the presence of a representative on committees critical to the state’s economic interests. But little has been done on this topic since. Indeed, Wendy Schiller’s study of the Senate, Parties and Rivals (2000), is the one significant piece of recent scholarship on state delegations, and it addresses topics on which Treul builds.

Changes, specifically the increasingly near-impregnable wall of partisanship that has grown since the work on House delegations was published provide part of the motivation for Treul’s work. Has the partisan rivalry that infects so much of what transpires—or does not—in the contemporary Congress made it impossible for those who represent a state but sit across the aisle from one another to work on behalf of their state? To answer the question, the author turns to two kinds of data. One approach is the traditional one of seeing how often members of a delegation vote together. The second approach measures the degree to which a state’s legislators sponsor legislation in the same issue area.

Unlike earlier works that explored delegation activity in a single chamber, Treul provides data on both the House and Senate and the interactions between members of the two bodies. After chapters that examine each chamber separately, in Chapter 5 she tests propositions concerning the cross-fertilization in which senators venture into policy areas already attracting the attention of some House members, especially representatives buoyed by ambition. Although it is not their intention, ambitious House members who embrace new issues serve as scouts for senators who have had less interaction with their constituents during the first four years of a term. Topics that have bolstered support for House members get the attention of senators eager to freshen up their policy résumés in anticipation of seeking reelection. It is the practice of members who suddenly expand their range of legislative initiatives by copying what their delegation colleagues in the other chamber are already doing that provides the book’s title—Agenda Crossover.

While this book may not succeed in reviving the study of congressional delegations, Treul makes the case that these entities serve a different function from their predecessors that were studied at a time before polarization became part of the everyday vocabulary. Previous students of House delegations stressed the ability to magnify a state’s influence by overcoming the collective-action problem and putting aside personal ambition to promote a state’s well-being. Today in both chambers, the motivation for cooperation—a motivation so strong that it sometimes overcomes the tidal wave of polarization—is reelection. Poaching the policy initiatives of one’s colleagues may provide an incumbent with a new appeal to voters. House members with progressive ambitions may offer initiatives in line with work done by the senator they hope to replace.

In the Senate, Schiller found that each member of a state’s dyad sought to create a unique identity by concentrating on issues different than those in the wheelhouse of his or her colleague. Treul concludes that today senators, especially when the two from a state share a party tie, often gravitate toward one another on roll-call votes and policy initiatives. The evidence is stronger for floor voting than for policy initiatives. Surprisingly, and in contrast with the past, senators from opposite parties but the same state now vote together on key roll calls as frequently as do senators who belong to the same party.

In terms of policy interests, senators from a state do not as frequently venture onto one another’s turf. Treul reports that sharing policy concerns has increased from the 5% observed by Schiller. But Treul’s graphs show little consistent change over the 32 years she studied, with the share of issue overlap for pairs of senators hovering around 15%. She apparently uses a different measure of agreement than Schiller did since Treul’s Figure 4.7 indicates agreement in the 101st Congress—the one analyzed by Schiller—at about 15%.

Although not the point emphasized by Treul, her work, along with Tracy Sulkin’s Issue Politics in Congress (2005), shows how campaigns lead members of Congress to expand their policy portfolios. Sulkin observes a learning curve and points to the experience of the campaign after which a legislator who is reelected may give attention to the issues raised by the challenger. Treul offers a more prospective perspective, arguing that in anticipation of a reelection campaign, an incumbent may seek out issues popular with the electorate and attempt to rally support by introducing legislation in that sphere. Adding sponsorship of legislation similar to that introduced by others in the delegation to a legislator’s own repertoire is a form of responsiveness to changes in public priorities.

Contrary to the belief that partisanship infects every legislative action, there are in fact limits to it. While Senator Bill Frist (R-TN) broke the norm that senators not seek to defeat a colleague when he campaigned against Minority Leader Tom Daschle (D-SD), a same-state rule limits such action. Treul provides anecdotal evidence that members of a delegation will not work to defeat their colleagues in the other party. This proposition is not tested empirically but rests largely on the behavior of the Wisconsin delegation, underscored by the criticisms of a Republican challenger outraged when delegation dean James Sensenbrenner (also Republican) refused to help him in an unsuccessful bid against a Democratic incumbent. It would be interesting to know how widespread that norm is.

Partisanship has reduced the frequency with which delegations meet to discuss issues. The 32 interviews Treul conducted with members and their staffs indicate that some state legislators convene in party groupings and not as a single unit. When Scott Brown replaced Ted Kennedy, Massachusetts Democrats continued to meet but never invited their lone GOP colleague.

Agenda Crossover provides us with new conceptual tools that suggest the continuing relevance of state delegations in an environment much changed from earlier studies. However, it leaves unanswered such questions as how regularly and closely a state’s senators and representatives work together to promote their state’s economy. Under what conditions do delegations successfully counter centrifugal partisan pull? Do concerns other than reelection prompt some legislators to pursue opportunities for cooperation? A lobbyist with whom I met recently identified several senators whom he referred to as “home state senators,” by which he meant individuals like Lindsay Graham (R-SC), Joe Manchin (D-WV), and Thad Cochran (R-MS), who concentrate on attracting and maintaining jobs on military bases and with government contractors in their states. For these legislators, every interaction begins with a discussion of how the lobbyist’s principal’s actions impact the state’s economy. Senators with this orientation probably have more extensive interactions with other members of the delegation than do senators mulling a presidential bid.

Treul revisits a venue long ignored by congressional scholars, the state delegation, and finds that its function today differs from that observed decades ago. The delegation now provides a setting for the exchange of ideas about what appeals to voters. The motivation for legislators to learn from one another is the strongest of all incentives—the desire for political survival.