The determinants of success of special interests in redistributive politics

We examine what determines whether an interest group will receive favors in pork-barrel politics, using a model of majority voting with two competing parties. Each group's membership is heterogeneous in its ideological affinity for the parties. Individuals face a trade-off between party affinity and their own transfer receipts. The model is general enough to yield two often-discussed but competing theories as special cases. If the parties are equally effective in delivering transfers to any group, then the outcome of the process conforms to the "swing voter" theory: both parties woo the groups that are politically central, and most willing to switch their votes in response to economic favors. If groups have party affinities, and each party is more effective in delivering favors to its own support group, then we can get the "machine politics" outcome, where each party favors its core support group. We derive these results theoretically, and illustrate their operation in particular examples.