RIO DE JANEIRO — South American leaders are watching closely as Brazil chooses a new president on Sunday, in a vote that could further chill relations on the continent or usher in a return to closer regional ties.
As leftist leaders have swept into office across Latin America in recent years, Brazil’s diplomatic relations with the region have cooled under the right-wing incumbent, Jair Bolsonaro, who has bashed many of his new peers.
Luiz Inácio Lula da Silva, the leftist vying to return as Brazil’s president, has promised to restore stronger relations with the country’s neighbors.
Mr. Bolsonaro has blamed Argentina’s left-wing government for mismanaging that country’s economy, hurled insults at Chile’s new leftist president and has urged voters to reject Mr. da Silva in order to stop Brazil from “turning into Venezuela.”
Brazil’s president “has used Latin America as a symbol of a leftist backslide,” said Esther Solano, an international relations professor at the Federal University of São Paulo. “Latin American communism is this common enemy, this boogeyman.”
Mr. Bolsonaro’s criticism has so badly strained relations between Brazil, Latin America’s biggest country, and its neighbors that many regional leaders are rooting for Mr. da Silva, known universally as Lula, according to two South American diplomats who spoke on the condition of anonymity to talk about the private discussions in their governments.
After Mr. da Silva emerged as the top vote-getter in the election’s first round on Oct. 2, President Alberto Fernández of Argentina wrote on Twitter: “I congratulate my dear Lula for his victory.”
During his two terms in office, from 2003 through 2010, Mr. da Silva pushed to deepen regional alliances, most notably through Mercosur, South America’s main political and trading bloc. The former unionist even proposed a single currency for the region, though the idea — deemed unviable by most experts — never got off the ground. Still, he has raised the idea again in his current campaign.
“He will do whatever it takes to reposition Brazil — like he did in the early 2000s — as a leader in South America,” said Guilherme Casarões, a political scientist at the Getúlio Vargas Foundation, a Brazil-based research institute.
Hussein Kalout, an international relations researcher at Harvard University who has participated in some of Mr. da Silva’s recent meetings with foreign officials, said that Mr. da Silva wants to increase cooperation with other Latin American countries around climate change.
“Brazil is totally adrift and isolated in its own region, and this is not good,” he said.
Mr. Bolsonaro, elected in 2018 on promises to place “Brazil above everything,” has taken a more isolationist approach, reducing regional trade and quitting regional bodies.
The outcome of Sunday’s election could also prove a crucial bellwether of Latin America’s political map. The right-wing populism that propelled Mr. Bolsonaro has largely petered out and a win for Mr. da Silva will likely cement the pivot to the left.
But a victory for Mr. Bolsonaro could reinvigorate the right, Mr. Casarões said.
“Either way, it’s going to be a game-changer,” he said.