bq. Using a large-N, geographically representative sample of U.S. adults, we conduct an experiment to assess how sponsorship influences ad effectiveness. We find that attack ads sponsored by unknown independent groups are more effective, on net, than ads sponsored by candidates.
From a forthcoming paper by Deborah Brooks and Michael Murov. The study has all the usual limitations of an experiment conducted within a survey. For example, no one was seeing the experiment’s ads in real life, and in fact, the ads were for a fictitious race. (Fiction is a technique sometimes used in experimental studies of campaign messages — for more on its advantages here, see p.12 of the paper.)
But the experiment did allow Brooks and Murov to isolate the one factor they care about most: who sponsors the ad.
Respondents to the survey first saw positive ads for each candidate, then a negative ad about one candidate. Respondents were randomly assigned to see a negative ad that had no sponsor identified, that was sponsored by the opposing candidate, or that was sponsored by a fictitious independent group (“Citizens for a Better State Government”). The content of the ad itself was the same, except for the sponsor.
Brooks and Murov find that the negative ad by the independent group was more effective. This is not because sponsorship by the independent group made the ad more persuasive. It’s because the candidate-sponsored negative ad generated backlash against the sponsoring candidate — a well-known risk to negative ads and one that may contribute to why negative ads don’t consistently help the candidate who airs them.
Of course, there are all sorts of reasons why we wouldn’t want to generalize too much from just this one study. Brooks and Murov discuss this at length in the conclusion. But as independent advertisements become more prominent post-Citizens United, this is surely a subject ripe for further research. As Brooks and Murov write:
bq. …although the present study is the first one to analyze how the public responds to attack television ads by unknown independent groups, it should not be the last.