Does money have a conservative bias? Estimating the causal impact of Citizens United on state legislative preferences

Recent work has suggested that the US Supreme Court’s ruling in Citizens United (2010), eliminating restrictions on independent campaign expenditures, increased the election probabilities of Republican state legislative candidates (Klumpp et al. in J Law Econ 59(1):1–43, 2016). Left unexplored has been whether the Court’s ruling in Citizens United increased not only the number of Republican state legislators, but also the conservatism of their estimated policy preferences, net of any effects on election probabilities. We attempt to distinguish between the possible electoral and preference effects of Citizens United. Our estimates consistently suggest that Citizens United led not only to greater likelihoods of election for Republican state legislative candidates, but also to larger within-district increases in their conservatism. The estimates, which are robust to a series of matching and placebo exercises, may provide support for the claim that more money in elections has contributed to greater conservatism among state-level Republican officeholders.