In late 2017, the first unified Republican government in 15 years enacted the Tax Cuts and Jobs Act, which cut taxes for corporations and the wealthy. Why did so many citizens support a policy that primarily benefited people richer than them? The self-interest hypothesis holds that individuals act upon the position they occupy in the income distribution: richer (poorer) taxpayers should favor (oppose) regressive policy. Associations between income and policy preferences are often inconsistent, however, suggesting that many citizens fail to connect their self-interest to taxation. Indeed, political psychologists have shown compellingly that citizens can be guided by partisan considerations not necessarily aligned with their own interests. This article assesses public support for the Tax Cuts and Jobs Act of 2017. Using data from the 2018 Cooperative Congressional Election Study as well as contemporaneous ANES and VOTER surveys to replicate our analyses, we show that self-interest and partisanship both come into play, but that partisanship matters more. Personal financial considerations, while less influential than party identification, are relevant for two groups of individuals: Republicans and the politically unsophisticated.