What does Brazil’s election mean for the United States?

Brazil’s presidential election on Sunday could reshape U.S. ties with Latin America’s biggest country, leading to increased tensions or bridging divides over trade, climate change and safeguarding democracy.

A victory by the far-right incumbent Jair Bolsonaro, who has questioned the electoral process and attacked institutions like Congress and the Supreme Court, could further strain an uneasy alliance at a time when democracy in the United States is also under strain.

The leftist challenger, Luiz Inácio Lula da Silva, a former president known widely as Lula, has vowed to protect Brazil’s young democracy, criticizing Mr. Bolsonaro over his baseless claims that the electoral system is rigged. Mr. da Silva’s own integrity, however, has been tarnished by his ties to past corruption scandal.

“This election is really at the center of the global democratic backsliding,” said Nicholas Zimmerman, who worked on Latin America policy in the Obama administration and is now a global fellow at the Wilson Center. “Washington is watching closely. Everyone has a lot of skin in the game.”

Mr. Bolsonaro has said that if he loses Sunday’s vote it would only be through fraud, fueling worries that he may challenge the result and call on his supporters to take to the streets and demand that he remain in power.

Such signals have unsettled Washington, prompting the Senate to pass a resolution last month urging a rupture of relations and military assistance to Brazil in the event of a coup.

Brazil’s relations with the United States have been rocky under Mr. Bolsonaro, who rose to power in 2018 as an anti-establishment candidate strikingly similar in style, tactics and rhetoric to former President Donald J. Trump.

The two leaders struck a fast alliance, bonding over a common disdain of the global climate agenda and “communist threats” like Venezuela. Mirroring a decision by Mr. Trump, Mr. Bolsonaro tried, though ultimately failed, to move Brazil’s embassy in Israel from Tel Aviv to Jerusalem.

But relations cooled after President Biden took office with Mr. Bolsonaro questioning the results of the election and hesitating to immediately recognize his victory.

Still, the two countries have found common ground in trade policy, with Washington pushing to accelerate Brazil’s bid for membership in the O.E.C.D, a 38-member bloc that includes some of the world’s largest economies.

“This process will continue if Bolsonaro is re-elected,” said Fernanda Magnotta, a professor of international relations at F.A.A.P., a Brazilian university and research institute. “But it’s not clear if it will be a priority for Lula.”

During his two terms in office, Mr. da Silva maintained friendly relations with Washington, but also favored trade alliances with Brazil’s neighbors, fostered close commercial ties with China and played a key role in multilateral blocs that excluded the United States.

But Mr. da Silva does share common goals with the United States around climate change, promising to tackle the destruction of the Amazon rainforest and create green jobs.

“It’s an issue that puts both Lula and Biden on the same page,” Ms. Magnotta said.