Earmarking taxes for specific expenditure categories is thought to be a crucial factor in the development of the early modern European fiscal states and remains a widespread, yet fiscally rigid and oftentimes inefficient, policy tool. I explore a decidedly political logic to the puzzling prevalence of tax earmarking. In this paper, I test an initial micro-behavioural condition for this political logic of earmarking: that general fund taxation may produce more political mobilization than earmarking would, threatening political survival of governments in low-capacity states.