Abstract
Bipartisanship and compromise are widely treated as hallmarks of effective democratic governance. Scholars document their erosion as evidence of democratic dysfunction, and reformers routinely advocate institutional changes designed to foster cross-party cooperation. Yet these assessments rest largely on evidence from a single institution: the United States Congress, characterized by narrow, frequently shifting majorities that make bipartisan coalition-building a practical necessity. Most American state legislatures look nothing like Congress. Many are governed by durable majorities that face little prospect of losing power, and in these settings, the conditions that make bipartisanship valuable in Congress may not apply.
This dissertation develops and tests a conditional theory of bipartisan collaboration using an original dataset spanning 43 state legislatures from 2009 to 2018, comprising more than 400,000 bills, and 5.1 million cosponsorship decisions. I argue that the value, consequences, and normative significance of cross-party cooperation depend fundamentally on whether majority parties must rely on minority votes to govern. Where that dependence exists, bipartisanship reflects genuine power-sharing and rewards legislators who invest in cross-party coalitions. Where it does not, collaboration persists but takes an asymmetric form I term selective reciprocity: minority legislators continue to invest in cross-party cooperation to build reputational capital and maintain legislative relevance, while majority legislators reciprocate selectively—engaging early in the legislative process and on low-stakes initiatives but withdrawing support when it would meaningfully constrain policy outcomes.
Three empirical chapters evaluate this framework. The first examines the relationship between bipartisan collaboration and legislative effectiveness, finding that bipartisanship predicts legislative success in competitive chambers but not where majority parties can govern unilaterally. In secure chambers, effective lawmakers are not those who work across the aisle but legislators who strategically manage intra-party ideological divisions, linking legislative success to partisan consolidation and narrowing the representational breadth of governing coalitions. The second chapter addresses a puzzle raised by the first: if bipartisan collaboration is not always necessary for success, why does it persist? I find that minority legislators are consistently bipartisan while majority legislators reciprocate selectively—cosponsoring minority party initiatives unlikely to advance, preserving the appearance of cooperation while protecting their policy agenda. The third chapter examines whether procedural rules shape bipartisan coalition-building, finding that across the many rules that structure various stages of the lawmaking process, formal rules bear no detectable relationship to cross-party collaboration. Political conditions, particularly electoral competition and majority party security, are far more consequential than the procedural architecture of a chamber.
Taken together, these findings reorient how we should evaluate legislative institutions and the representation they produce. The normative and empirical significance of bipartisanship is inseparable from electoral competition. Where competition is present, cross-party cooperation reflects genuine power-sharing and facilitates broadly representative outcomes. Where it is absent, bipartisanship is performative rather than consequential, obscuring the concentration of policymaking power within the majority party and rendering illusory the representational breadth it is assumed to deliver. Bipartisanship persists, but it is selective in form, asymmetrical in effect, and structured by the institutional advantages of majority control.
