Individual campaign contributions in a Downsian model: expressive and instrumental motives

We investigate in a Downsian framework the possibility of and rationale for individual campaign contributions under various combinations of voters’ and candidates’ objective functions. We first show in a simple voting model that expressive motives might give rise to contributions and separated positions, while instrumental motives will not. We then show in a probabilistic voting model that both motives could lead to giving and policy divergence. However, when this is the case, positions are more separated, contributions are greater, and society’s welfare is higher when motives are expressive than when motives are instrumental.