Complementing recent theoretical models of tax competition with endogenous leadership, we empirically model local policy diffusion as a dynamic asymmetric process. Using a setting where local option sales taxes rapidly transitioned from nonexistence to ubiquity, we construct a policy leadership index to classify jurisdictions as leaders or followers. Using models that control for vertical tax competition effects, we show how asymmetric leader–follower dynamics characterize horizontal tax competition over the three decades that follow. A placebo test further supports our main conclusions. This methodological approach could be adapted to other settings where policies exhibit both extensive and intensive margins.