Brazilian election case proves social media’s danger to democracy

Misinformation on social media played a troubling role in propelling far-right Congressman Jair Bolsonaro to the Brazilian presidency. While it would be inaccurate to say that Mr. Bolsonaro won 55 percent of votes thanks to misinformation alone, his chances were certainly boosted by the spreading of fake news on WhatsApp Messenger and Facebook.

It is important to note that it was the powerful desire for political change in Brazil–after a drawn-out corruption scandal and a court decision compelling the jailed front-runner Luiz Inácio Lula da Silva to withdraw from the race—which initially opened the door for Jair Bolsonaro to win the election. But Mr. Bolsonaro’s candidacy also benefited from a powerful and coordinated disinformation campaign intended to discredit his rivals, according to the Brazilian newspaper Folha de S.Paulo.

Days before the October 28 runoff between Mr. Bolsonaro and his center-left opponent Fernando Haddad, an investigation by Folha de S.Paulo revealed that a conservative Brazilian business lobby had bankrolled the multimillion-dollar smear campaign—conduct which may constitute illegal campaign financing.

Bolsonaro election scandal fallout

Using WhatsApp, a Facebook-owned messaging service, Mr. Bolsonaro’s supporters delivered an onslaught of daily misinformation straight to millions of Brazilians’ mobile phones.

They included doctored photos portraying senior Workers’ Party members celebrating with Communist Fidel Castro after the Cuban Revolution, audio clips manipulated to misrepresent Haddad’s policies and fake “fact-checks” discrediting authentic news stories.

The misinformation strategy was effective because WhatsApp is an essential communication tool in Brazil, used by 120 million of its 210 million citizens. As WhatsApp text messages are...