This project is an examination of patterns of state policy adoption, and provides a new theory for policy diffusion research. While traditional policy diffusion research focuses on geographic proximity as the main mechanism for policy adoption, I argue that states are more likely to rely on partisan proximity and adopt policy from partisan neighbors. This is, primarily, a result of heightened polarization nationally. In the absence of national policymaking, states will feel both more pressure to create more policy as well as leeway to enact more partisan policies. In order to test this theory, I look at three cases: same-sex marriage, right-to-work, and state lottery adoption. I utilize interviews with state lawmakers and interest group staff as well as quantitative methods to show the relationship between partisanship and policy diffusion. Overall, this work adds an important element to a vast and well-established literature and provides a new way of understanding the policy creation in the American states.