My book, entitled Strange Bedfellows: Interest Group Coalitions, Diverse Resources, and Influence in American Social Policy (Cambridge University Press), is motivated by a simple question with broad implications for American democracy: how do interest groups that advocate for the poor gain influence in the contemporary U.S. Congress? Although policy scholarship identifies advocates for the poor as influential in the policymaking process, existing political science theories cannot explain how interest groups with limited budgets and small membership bases influence the policy choices of elected legislators. In this book, I reconcile this disconnect between political science and policy scholarship by focusing theoretical and empirical attention on the collaborative lobbying strategies of interest groups. I develop a new theory of influence that explains how and when coalitions gain influence, and provide empirical support for the theory through an analysis of interest group collaboration preceding the 1996 welfare reform law, one of the most significant social policy changes in recent history. In a departure from existing work, I theorize that influence derives from a set of groups lobbying collaboratively rather than an interest group lobbying independently. By shifting the analytic focus away from the individual group and toward a set of groups, the theory explains how groups with limited resources gain influence despite their resource limitations. Moreover, because the theory has implications across policy domains, the book offers a framework for understanding the broader role of coalitions, which are increasingly used by all types of interest groups in their attempts to gain influence in American politics.