Persuading voters is a key challenge in elections. One tactic often used by political candidates to have voters side with their position is to employ political ads during their campaigns. A political ad can be positive in that it focuses solely on a given candidate, meaning that both an opponent and the sponsor are identified, but a political ad can also be negative, whereby it criticizes an opponent and mentions the sponsor only at the end of the ad, or indirectly, or not at all. The last type of ad is usually frowned upon by most voters and has no real immediate effect on their attitudes regarding the political issue raised in the ad. Nevertheless, a negative ad can have a delayed persuasive effect on ...