15 April 2020

Positive Spillovers from Negative Campaigning

In a field experiment, the authors analyze the spillover of a candidate vilifying his opponents in an election campaign. Resulting positive spillover effects are observed for the third, idle candidate. The candidate running the negative ad is perceived as less cooperative, less likely to lead a successful government, and politically more extreme.

Key issue

Negative advertising in electoral campaigns is on the rise. Political strategists continue to advise candidates to vilify their opponents, but the academic debate on the effectiveness of this in persuading voters is still open. Negativity reduces the voters’ evaluation of the targeted politician, but may also have a backlash effect, by worsening the evaluation of the attacker. When there are more than two challengers in the electoral race, these two effects may create a positive spillover for other candidates who choose not to go negative.

Approach and methodology

We designed a large field experiment during an electoral campaign for mayor of a city in Italy and a survey experiment in a fictitious electoral campaign for mayor to test for the existence of this positive spillover from negative campaigning in favor of an idle candidate.

The field experiment, run during a multi-candidate electoral race, offers a real proving ground for our hypothesis. Our treatments consisted of canvassing: volunteers of one of the challengers met with voters in person or distributed flyers providing either a positive or a negative message. We study the effect of these treatments on the actual electoral outcome. We find a strong, positive spillover effect on the idle candidate, whose vote share increases by 3.7 percentage points when the incumbent was targeted with a negative ad by the other challenger.

Key findings and conclusions

In the survey experiment, we construct a controlled environment with no ideological components and no concerns for strategic voting. Voters in this election were the respondents of an online survey, who were told to consider that they just moved to a town with an upcoming mayoral election between an incumbent and one or two opponents, with similar individual characteristics and no ideological difference. They were shown a video ad from each of the candidates, with a positive message for the incumbent and one of the opponents, whereas the campaign of the other opponent was randomized with a negative or positive message. The empirical evidence confirms the existence of a strong, positive spillover effect in favor of the idle candidate. We also find a sizable backlash effect. The candidate running the negative ad was perceived as less cooperative, less likely to lead a successful government, and politically more extreme.