Disclaimer. Don't rely on these old notes in lieu of reading the literature, but they can jog your memory. As a grad student long ago, my peers and I collaborated to write and exchange summaries of political science research. I posted them to a wiki-style website. "Wikisum" is now dead but archived here. I cannot vouch for these notes' accuracy, nor can I even say who wrote them. If you have more recent summaries to add to this collection, send them my way I guess. Sorry for the ads; they cover the costs of keeping this online.
Freedman, Franz, and Goldstein. 2004. Campaign advertising and democratic citizenship. AJPS 48:723-741.
Though our theories say that debates, news, speeches, and so on are all good for democracy, we often malign candidate advertisements. The authors disagree: Candidate ads also provide meaningful information, and they simultaneously provide useful emotional cues (cf. Brader 2005). People who see these ads, then, should be more informed than other people; this effect is especially strong among those who have the least information about politics to begin with.
They find modest evidence in their favor: "Specifically, our findings show that exposure to campaign advertising produces citizens who are more interested in the election, have more to say about the candidates, are more familiar with who is running, and ultimately, are more likely to vote."
Research on similar subjects