Studies of policy diffusion often focus on the horizontal spread of enactments from one state to another, paying little or no attention to the effects of local laws on state-level adoptions. For example, scholars have not tested whether local policy adoptions make state action more likely (through a snowball effect) or less likely (through a pressure valve effect). This study conducts the first comprehensive analysis of vertical policy diffusion from city governments to state governments, while simultaneously examining the influence of state-to-state and national-to-state diffusion. Focusing on three different types of antismoking laws, we find evidence that policies do bubble up from city governments to state governments. State politics are crucial to this relationship, however, as local-to-state diffusion is contingent on the level of legislative professionalism and the strength of health advocates in the state.