Conflict on the campaign trail? How campaign effort and electoral competitiveness shape affective polarization

Concerns about the consequences of affective polarization for governing and democracy have resulted in a strong surge of publications on the topic. This literature has already provided much insight into the individual-level correlates of affective polarization, but we know much less about how the political context in which voters choose can contribute to affective polarization. We theorize that the intensity of election campaigns increases affective polarization, which we capture through indicators of (a) campaign spending, from both in-parties and out-parties, and (b) electoral competitiveness. Using the British case and leveraging within-country and over-time variation in these indicators, we find support for our expectations. Specifically, we show first that in-party spending is positively associated with affective polarization, leading both to increased in-party like and out-party dislike. Second, we show that competitiveness is positively associated with out-party dislike—individuals who experience more competitive electoral contests grow to dislike parties that they compete with to a greater degree. We contend that this mechanism could contribute to the within-country variations in affective polarization found in previous research.