Does disagreement stimulate political participation, or discourage it? Some researchers find that exposure to cross-cutting views demobilizes voters. Selection bias in the way individuals expose themselves to disagreement and other sources of endogeneity pose challenges to causal inference. The author addresses these concerns by using an experimental design that exogenously assigns cross-cutting or reinforcing messages.

A random sample of North Carolina Democrats and Republicans received postcards summarizing either liberal or conservative opinions on a statewide same-sex marriage amendment. The author finds that individuals exposed to disagreement demobilize by 1.0 to 1.6 percentage points, with the majority of the combined effect attributable to a 2.0-percentage point decrease in turnout among Republicans receiving a Democratic message. The author observes a similar level of demobilization when defining disagreement on the basis of predicted issue position on same-sex marriage in place of partisan affiliation. The effects are strongest among moderate supporters of traditional marriage that receive a cross-cutting treatment. The experimental design thus enables causal evidence on the nuanced interactions between political or issue position and exposure to campaign information from the opposing side.