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).

Instagram has exploded in popularity since 2016. One reason is that people are tiring of Facebook’s cluttered interface and cumbersome privacy controls. Instagram offers pretty pictures and is easy to use. What supercharged its growth was the introduction, in late 2016, of “Stories”—a parallel feed of pictures and videos that disappear after a day. While the “grid”, as the traditional Instagram profile is known, was painstakingly curated by its users to present their best lives, Stories gave them licence to have some fun, safe in the knowledge that the posts would not linger.

Usage shot up, particularly among older people. In June 2016 Instagram had 500m users. That had grown to 1bn by June 2018; about half of American members of Congress and nearly three-quarters of senators had signed up. It is safe to assume all those numbers are now much higher. Moreover, engagement levels are stratospheric. Instagram’s tenth-biggest account gets three times as many interactions as Facebook’s single-biggest, according to Axios, a politics website.

Stories has changed Instagram. It introduced text to what had been a visual medium. And it gave users the ability to reshare others’ posts more easily. This combination of text and sharing, along with a huge user base, has made Instagram much more like Facebook—and irresistible to propagandists. Best of all, it is still regarded as a place for harmless snaps of sunsets, coffee cups and attractive young “influencers” flogging lip gloss, so users lower their guard.

But politics long ago infected Instagram. Its role in America’s election in 2016 was understated, says a report commissioned by the Senate Intelligence Committee. The report adds that in 2017 Russian propagandists shifted focus to Instagram after media coverage of their Facebook and Twitter operations. A report from New York University warns that Instagram will be “the vehicle of choice for people who wish to disseminate meme-based disinformation” in the election in 2020, noting that “beyond Russian interference, domestically generated hoaxes and conspiracy theories increasingly are thriving on Instagram.”

Already, accounts dedicated to divisive issues, such as political memes or vaccinations, have proliferated. Followers are then shown similar accounts, algorithmically reinforcing opinions just as Facebook’s news feed pushed extreme stories. Users are also finding ways to bring politics into the grid, such as changing their profile pictures to red in support of Kashmir, or blue for Sudan.

Since 2016 Facebook has linked up with fact-checking agencies, hired thousands of content moderators and tried to reduce the spread of inflammatory material. Its smaller, faster-growing social network has fewer safeguards. All the warning signs are there. Yet it may take another fall from grace, in another election, before anybody pays attention.

This article appeared in the International section of the print edition under the headline “The real influencers”