The purpose of this thesis is to present a network theory of public policy, and a kind of policy analysis that might be relevant for understanding governance and how stakeholders’ governance may influence policy outputs. To do so, I define policy networks as a set of stable relationships of interdependency among stakeholders, based on a framework composed of policy processes, sets of issues, types of stakeholders, and relational ties. Then, I present a theory of political power based on the inclusion/exclusion of stakeholders representing rival/competing interests, and on their position within a policy network. To empirically test it, I utilize the affiliation tie—formed when interest groups participated as witnesses in public hearings—to measure the influence of representative policy networks in the approval of important legislation in the mortgage and agricultural policies between 2005 and 2014. Besides, I utilize a socio-metric survey and interviews to infer the existence of each policy network. The findings confirm that—regardless of the party which won the elections—the struggle among rival/competing interests present within policy networks shapes decisions in Congress. Policy networks have become an important form of exercising political power in our society, and an essential part of our democracy.