FACEBOOK WAS a breeding-ground for partisanship, crackpot articles and conspiracy theories long before America’s presidential election in 2016. The social network is optimised for “engagement”, and encourages people to keep scrolling, clicking and commenting by promoting content that triggers strong reactions. Yet it took the revelation of a massive Russian propaganda campaign before lawmakers, journalists and Facebook users began to take notice of the risks this entails. Something similar will happen with the election in 2020—but this time to Instagram (which is owned by Facebook).