California Journal of Politics and Policy

Advertising studies commonly examine the effects of one-sided treatments. However, political communication campaigns are competitive environments where voters are likely to hear more than one perspective. Because of this dynamic, the persuasive effects of single-sided ads may be less likely to hold in a competitive environment. When respondents are exposed to arguments from both sides of a ballot proposition issue, can the disclosure of a credible group help an advertisement overcome prior opinions? I address this question using a randomized experiment that includes ballot proposition campaign ads. In the experiments, I manipulate the pretreatment environment by exposing some respondents to a newspaper editorial in order to provide them with prior opinions that might cause them to resist subsequent advertisements. I also vary the presence or absence of campaign finance disclosure within the advertisements. In all cases, the presence of a credible editorial is associated with a change in support for the initiative. However, the use of a credible campaign finance disclosure has a far less consistent effect. While campaign finance disclosures from credible groups can help counteract prior beliefs that citizens may hold, I find that the magnitude of these changes is somewhat small.