Does campaign spending work? Field experiments provide evidence and suggest new theory

This article reports the results of several field experiments designed to measure campaign effects in partisan contests. The findings suggest incumbent campaigns failed to increase incumbent vote share, whereas the challenger campaign was effective. To understand these and other results, the incumbent's optimal spending strategy was analyzed theoretically. The analysis reveals that if incumbents maximize their probability of victory rather than vote share, campaigns by typical incumbents are expected to produce only minimal improvement in incumbent vote share. The analysis also explains how returns to campaign spending vary with the competitiveness of the election, how incumbent spending can improve the incumbent's probability of victory yet have only minimal effect on incumbent vote share, and why rational spending plans might decrease the sponsor's expected vote. This article demonstrates the wide scope of application for field experiments and provides an example of how experimental findings can serve as a catalyst for generating theories.