Political advertising, especially negative advertising, is a prominent feature of contemporary political campaigns in the United States. Campaigns use advertising strategically to persuade citizens their candidate is preferable to the alternatives; to mobilize like-minded supporters to get out to the polls to cast a ballot for their candidate; and to acquire citizen-personal information, so they can more effectively target individuals with appropriate persuasive or mobilizing messages. Online advertising is growing, but television advertising volume has largely been on the rise, too, with 2014 being a plateau. Evidence about trends in advertising content and effects of advertising on citizens come from television advertising in particular.
Over the past decade, candidates have consistently sponsored a majority of advertising on the airwaves although their share does appear to be declining in legislative races. Interest group sponsorship of political advertising has grown, especially in Senate and presidential races, taking advantage of recent legal changes in the campaign finance landscape. Negativity is the dominant form of television advertising, constituting more than 65% and as much as 75% of all congressional general election ads (and as much as 87% of presidential ads) on air since 2006. Parties and interest group sponsors are more likely to air negative advertising by candidates, but candidates do not refrain from going negative. In fact, candidate negativity comprises roughly half of all negative ads on air. Negative ads are more likely to cite specific sources and therefore are generally considered more substantive. TV advertising is unlikely to contain partisan or ideological cues, in part, because it is targeted at swing voters.
Early studies of advertising cast doubt on their effectiveness, but more recent work suggests that advertising effects are small (mattering at the margin in the most competitive contests) and often conditional. That is, advertising effects often vary in relation to characteristics of the messages being aired, the individuals who view them, and contextual factors relating to the campaign more generally. Scholarship suggests that advertising has persuasive but short-lived influence on citizens and that advertising volume and negativity may aid mobilization efforts (although the influence of negativity may be conditioned upon ad characteristics and timing).
Technological advances in the way TV advertising is deployed is increasing campaigns ability to target citizens in a fashion similar to online advertising, which has implications for how well researchers can continue to study it. Scholars have made considerable progress in studying 21st-century advertising effects, but a number of logistical hurdles and unanswered research questions remain.