Polls had suggested that the candidate, Wilson Witzel, a retired federal judge and military veteran running for governor of Rio de Janeiro, had no shot at victory over his better-known opponent. But with Mr. Bolsonaro’s backing, Mr. Witzel won 41 percent of the vote, more than twice his opponent’s tally.
As they took stock of the new political landscape, political scientists and academics said Monday that the Bolsonaro phenomenon may have forever changed how campaigns are run in Brazil.
Unlike rivals who had far more time on national television — which is awarded based on party size — and who bought polished ads, Mr. Bolsonaro ran a scrappy, inexpensive campaign powered mainly by social media. Supporters created hundreds of group chats on the messaging app WhatsApp, which the vast majority of Brazilians use, sharing campaign information, jokes, memes and conspiracy theories.
Victor Piaia, a sociologist who studies political communication at the State University in Rio de Janeiro, said it was unclear how much the campaign had coordinated with chat groups. But he said it was clear it had played a role in steering the narratives and benefited from the platform’s message-amplifying effect.
“This type of communication is less top-down,” said Mr. Piaia. “Everyone is the curator of their own content, and this makes the information distributed there more appealing.”
Mr. Piaia said he was especially surprised at how successful the Bolsonaro campaign was in directing down-ballot votes. While other political parties were handing out pamphlets on the streets, it spent weeks distributing a message with the names of candidates it supported through WhatsApp groups.
Among the biggest losers on Sunday were elected officials who have been embroiled in the far-ranging corruption investigation known as Lava Jato, or Car Wash. According to the newspaper Folha de São Paulo, 47 politicians who have been charged with corruption, or are being investigated, were not re-elected.