Sleeper Effect in Political Campaigns
In political campaigns during elections, voters often see negative advertisements about a party or candidate for office.
At the end of the advertisement, there sometimes is a notice that the opposing candidate or party paid for the advertisement. One would expect this would make voters question the truthfulness of such advertisement, and consequently and that they would not be persuaded.
However, due to the sleeper effect, even though the source of the advertisement clearly lacked credibility, voters have been found to be more likely to be persuaded later (and ultimately, vote against the candidate disfavored by the advertisement).