Published online by Cambridge University Press: 25 January 2021
Fiorina (1992, 1994) argued that increased professionalism of state legislatures in the 1970s and 1980s increased Democratic control of those bodies. While some subsequent empirical studies have been consistent with this hypothesis, doubt remains about the causal connection of this relationship. Our review of Fiorina's theoretical argument leads us to add legislative district size as a conditioning element to the model. Using data from state legislatures in 1960-98, we find that such a model supports the claim that the empirical connection between legislative professionalism and Democratic electoral success is causal and not spurious.