The Trump campaign sent targeted ads to Black people in 2016 to deter them from voting, according to an investigation published this week by Channel 4 in the U.K. The campaign denies this, but targeted digital advertising is a big part of political campaigns. So big that Google banned microtargeting in political ads; Twitter banned political ads completely. Facebook has not. How effective are targeted ads? If they can change a vote, should they be allowed? Molly speaks with John Deighton, a professor at Harvard Business School. His research focuses on digital and direct marketing. He says targeted advertising works, but it’s not the real problem.