The future of Brazil-Argentina relations

Heads of state from around Latin America will be gathered today in Buenos Aires, as Alberto Fernández takes office as the new president of Argentina. There is one notable absence, however: Brazil’s far-right President Jair Bolsonaro. Despite the close relationship the two countries have enjoyed in the past, Mr. Bolsonaro was not so fond of the guest list, which includes Venezuela’s authoritarian President Nicolás Maduro, and Cuba’s head of state Miguel Díaz-Canel.

There is also no love lost between Messrs. Bolsonaro and Fernández.

The former has called his counterpart a “leftist criminal,” while the latter teased the Brazilian government on social media by posting messages in support of Luiz Inácio Lula da Silva, the former Brazilian president and Mr. Bolsonaro’s political nemesis. At last week’s Mercosur Summit in southern Brazil, the two avoided shaking hands.

After toying with the idea of not having a single representative in Buenos Aires, Mr. Bolsonaro ended up sending Vice President Hamilton Mourão to the ceremony—thus avoiding further deterioration of what already seems like a dysfunctional relationship.

Even if the two countries have at times pursued different goals, Brazil and Argentina have followed similar paths in recent...