We study a political contest where two candidates advertise on a platform to persuade voters to vote in their favor. Voters a priori favor one of the candidates. The extent of a candidate’s favorability can be ascertained by a data intermediary who can decide to sell this information to one, both or neither of the candidates. We contrast the intermediary’s incentives for selling information with the platform’s incentives for maximizing candidates’ advertising expenditures, and show that the two are always at conflict. Our findings suggest that tensions may exist between social-media platforms, which often generate data that an intermediary may collect, and an intermediary whose data sale choice can lower the platform’s profit from advertisements. We characterize conditions under which the intermediary can influence the outcome of the contest.

我们研究了一场政治竞赛，其中两名候选人在一个平台上做广告，以说服选民投票支持他们的投票。先验选民青睐候选人之一。数据中介可以确定候选人的好感程度，可以决定将该信息出售给一个或两个候选人，也可以不出售给两个候选人。我们将中介机构出售信息的动机与平台使候选人的广告支出最大化的动机进行了对比，并表明两者始终存在冲突。我们的发现表明，社交媒体平台之间经常存在紧张关系，后者通常会生成中间人可能收集的数据，而中间人的数据销售选择会降低平台从广告中获得的利润。我们描述了中介可以影响比赛结果的条件。