https://www.wired.com/story/facebook-political-ad-system-designed-polarize/

Amid the tense debate over online political advertising, it may seem strange to worry that Facebook gives campaigns too little control over whom their ads target. Yet that’s the implication of a study released this week by a team of researchers at Northeastern University, the University of Southern California, and the progressive nonprofit Upturn. By moonlighting as political advertisers, they found that Facebook’s algorithms make it harder and more expensive for a campaign to get its message in front of users who don’t already agree with them—even if they’re trying to.

Social media is well on its way to supplanting television as the dominant platform for campaign spending. The study notes that online spending is projected to make up 28 percent of all political marketing in the 2020 elections, up from 20 percent just last year. The optimistic take is that this shift is helping campaigns, especially smaller ones, to more efficiently get their messages to the right voters. But the new study suggests that there are some limits to that account. By optimizing for what it defines as “relevance,” Facebook puts its thumb on the scale in favor of a certain kind of political communication, the kind that focuses on engaging with people who are already on your side. Polarization, in other words, is part of the business model.