Abstract
American political parties frequently advance contradictory arguments in policy debates, but scholars know relatively little about where these arguments originate. Outside research-producing institutions are likely culprits. Have the research and advocacy efforts of these groups helped structure policy discussions along party lines, thereby contributing to partisan polarization? I answer this question by tracing the diffusion of policy language related to cap-and-trade regulations across actors and over time. Utilizing quantitative network and text analysis techniques, as well as qualitative textual analysis, I find that outside groups inform policy discussions through their early research. First, prominent organizations develop ideas and talking points that then spread to other groups. Second, members of Congress adopt these talking points and use them to justify their views to their constituents. Importantly, the diffusion of arguments is most likely among actors with shared partisan commitments, resulting in two relatively cohesive and distinct partisan communities that advance partisan policy narratives. These findings have important implications for our understanding of partisan polarization, outside group influence, and the capacity for Congress to address meaningful public problems.