With the federal government and most states limiting or prohibiting individual, corporate, and union contributions to campaigns, reformers are turning their attention to the public financing of campaigns. While partial financing of campaigns already exists in several states, only a handful have enacted so-called “clean elections” laws, which completely fund the campaigns of participating candidates and require that these candidates raise no additional funds. We argue that such reforms are being adopted without sufficient attention to scientific studies, which to date find little to no systematic impact of existing funding programs. In this paper, we discuss what we know--and don’t know--about public financing, and how scientific inquiry can inform the normative debate on campaign finance reform.