Abstract: Although historical debates about the separation of powers focus on Congress, the President, and the Judiciary, in modern times, the bureaucracy is the elephant in the room. In a world of seemingly inevitable widespread congressional delegation to administrative agencies, as well as the Supreme Court’s blessing of independent agencies, how exactly is the fourth branch of government to be controlled? The canonical answer in administrative law, constitutional law, and political science, is agency design. By carefully selecting structural features of administrative agencies and requiring the use of specific decision-making procedures for policymaking, the legislature and the executive can ensure responsive and accountable bureaucracy—or so the argument goes. As Congress continues to create ever more agencies using ever more variations in institutional structure, and as the Supreme Court continues to grapple with which features of administrative are constitutional, the stakes of these conceptual debates have risen steadily. Indeed, we are in the midst of something of an agency design renaissance—a time period of fundamental change with respect to the federal bureaucracy—deriving mainly, although not exclusively, from the emergence of new administrative forms. Unfortunately, there is virtually no empirical scholarship that demonstrates a link between agency design and political responsiveness or agency behavior. This is due not to a lack of attention but to a fundamental problem of research design and the institutional landscape of administrative agencies. To address this question, scholars have studied individual agencies to document political influence exerted by Congress or the president in a specific policy domain. Such studies of individual agencies are important, but also analytically incapable of identifying the role of agency design in political responsiveness for two reasons. First, the relevant institutional features almost never vary within a single agency. Second, most policy outputs—where one would look to see evidence of political control—are not readily comparable across agencies. As a consequence, there has been little quantitative scholarship that establishes a link between agency design and a similar agency output across agencies or over time. This Essay focuses on an activity common to and comparable across many agencies—the distribution of federal moneys—to answer one of the most basic questions for agency design. We show that a prominent structural feature of agency design— the extent of high-level personnel politicization—affects the degree of political responsiveness by agencies