In 2010 Prime Minister Stephen Harper quietly created a system of Minister's Caucus Advisory Committees (MCACs), requiring ministers to consult with their backbench colleagues before taking policy proposals to cabinet. Based on interviews with Conservative MPs, ministers, political staffers and public servants, the paper argues that MCACs increase MPs' influence over government policy and enhance cohesion within the government's parliamentary caucus. By constraining ministers' policy freedom and providing the prime minister with regular political intelligence concerning policy proposals, MCACs reinforce his pre-eminence within cabinet and represent a significant innovation in the relationship between the executive and government caucus.