Facebook Political Ads And Accountability: Outside Groups Are Most Negative, Especially When Disappearing Or Hiding Donors

The emergence of online political advertising has come with little regulation, allowing political advertisers on social media to avoid accountability. We analyze how transparency deficits caused by dark money and group impermanence relate to the sentiment of political ads on Facebook. We obtained 525,796 ads with FEC-registered advertisers from Facebook's ad library that ran between August-November 2018. We compare ads run by candidates, parties, and outside groups, which we classify by (i) their donor transparency (dark money or disclosed) and (ii) the group's permanence (disappearing after 2018 or re-registering). Ads run by dark money and disappearing outside groups were more negative than transparent and re-registering groups, respectively. Outside groups as a whole also ran more negative ads than candidates and parties. These results suggest that transparency for political speech is associated with advertising tone: the most negative advertising comes from organizations with less donor disclosure and permanence.