Brazil’s election could shift influence between Argentina and its larger neighbor. Javier Milei may gain an ideological ally, but could also compete with Flávio Bolsonaro for Donald Trump’s attention. Flávio, a senator and eldest son of former president Jair Bolsonaro, was due to face President Lula on Sunday. Milei has openly backed him. His relations with Lula have collapsed.
The possibility of a Bolsonaro victory has drawn attention in Buenos Aires. Brazil’s larger population and economy could give its next government more weight in Washington. An analysis published by iProfesional on Saturday 3 October, by political writer Mariano Obarrio and based on sources in Argentina’s foreign ministry, quoted one source saying: “If Bolsonaro wins, the United States will give more room to Bolsonaro than to Milei.” The source pointed to Brazil’s size: “Brazil weighs more as a country and because of the size of its economy.”
The contest for Washington’s attention
Brazil has about 213 million people, more than four times Argentina’s population, and the largest economy in Latin America. That scale fuels concerns in Buenos Aires about whether Milei would keep his special standing with Trump if Flávio Bolsonaro took office. Unnamed Argentine officials made the assessment; it wasn’t a signal from the U.S. government.
A separate analysis by Argentine outlet TotalNews made a similar point, quoting Benjamin Gedan of the Stimson Center, a Washington think tank. Gedan, a former White House adviser on South America, called Flávio “as MAGA as Milei” and said he was “equally committed” to becoming Washington’s main South American ally. Flávio has promised Brazil would join the Shield of the Americas, a U.S.-led security initiative Argentina already belongs to.
Trump hadn’t endorsed Flávio Bolsonaro, Time reported, though he called Brazil’s vote very important. That distinction matters: iProfesional describes a forecast by Argentine officials, not evidence that Washington has chosen between the two politicians. The potential shift concerns competition for U.S. attention and influence, not a confirmed change in American policy.
Diplomatic ties and trade
Milei joined Flávio Bolsonaro’s campaign launch in São Paulo on 25 July. La Nación reported that he called Flávio a friend and Lula a “thief.” In August, Brazil downgraded its diplomatic representation in Buenos Aires. La Nación reported that neither ambassador had returned to post.
Flávio has also appealed directly to Argentina. In June, he promised Brazil would “return to being a brother to Argentina.” His economic coordinator, Daniella Marques, said his plan draws on Milei’s approach. A Bolsonaro victory could end the diplomatic freeze; a Lula victory would leave Milei facing a neighbor he’s repeatedly insulted.
The economic relationship gives both governments reason to repair ties. Two-way trade reached US$31.2 billion in 2025, a 13-year high, according to the Rosario Board of Trade. Argentina exported US$12.8 billion in goods to Brazil and imported US$18.4 billion, leaving a deficit of about US$5.7 billion. Cars, car parts, wheat and fuel account for much of the trade, Forbes Argentina reported.
Brazil’s polls were scheduled to close at 17:00 Brasília time, also 17:00 in Buenos Aires and 20:00 UTC. No candidate could win outright without more than half the valid votes. If none did, the top two would meet again on 25 October.