Political contribution caps and lobby formation: Theory and evidence

The perceived importance of “special interest group” money in election campaigns motivates widespread use of caps on allowable contributions. We present a bargaining model in which the effect of a cap that is not too stringent on the amount a lobby can contribute improves its bargaining position relative to the politician. It thus increases the payoff from lobbying, which will therefore increase the equilibrium number of lobbies when lobby formation is endogenous. Caps may then also increase aggregate contributions from lobbies and increase politically motivated government spending. We present empirical evidence from U.S. states that support various predictions of the model. We find a positive effect on the number of PACs formed from enacting laws constraining PAC contributions. Moreover, the estimated effect is non-linear, as predicted by the theoretical model. Very stringent caps reduce the number of PACs, but as the cap increases above a threshold level, the effect becomes positive. Contribution caps in the majority of U.S. states are above this threshold.