Diffusion of a policy innovation from one state to another is an important component of social change. Several theories and models have been developed to explain how and under what circumstances policy innovation and diffusion occurs. This paper examines the policy diffusion process through the case of Individual Development Accounts (IDAs), a policy innovation designed to provide matched saving opportunities for low-income people to accumulate assets. While our examination supports several of the prominent theories of policy diffusion, we suggest that a fusion of policy theories may better guide policy makers in more adequately predicting and executing the diffusion of policy innovation. Furthermore, these theories appear to hold most relevance at distinct stages of the process.