When and why do sub-optimal agricultural policies persist despite technical evidence highlighting alternatives? And what explains episodes of reform after prolonged periods of policy inertia? This paper addresses these questions by applying the Kaleidoscope Model for agricultural and food security policy change to the specific case of agricultural input policy in Zambia. Since 2002, the Farmer Input Support Program (FISP) (formerly the Fertilizer Support Program, FSP) has been a major cornerstone of Zambia’s agricultural policy. Over the years, however, many researchers have highlighted weaknesses with the program and proposed other options.