Argentine President Javier Milei suffered a decisive electoral defeat in Buenos Aires Province, with his La Libertad Avanza party securing just 34% of the vote compared to 47% for the centre-left Fuerza Patria coalition, according to official results data with 91% of ballots counted.

The outcome dealt an unexpected blow to Milei's government, given Buenos Aires Province's outsized political importance. The capital region contributes over 30% of Argentina's GDP and accounts for 40% of eligible voters nationwide, making it a crucial electoral bellwether, AFP reported. The election renewed 23 Senate seats and 46 legislative positions.

Turnout reached approximately 63%, contradicting expectations that voter disenchantment might lead to abstentions. Instead, Ámbito noted that dissatisfaction translated into "punishment votes" against the incumbent. Peronism, unified under the Fuerza Patria banner despite months of internal strife, reasserted its dominance in Argentina's most populous district.

Governor Axel Kicillof, in particular, emerged strengthened from the victory, positioning himself as a potential presidential contender for 2027.

"It is a crushing victory, thanks to Sergio (Massa) and Cristina (Fernández de Kirchner), unjustly condemned, who should be on this stage," Kicillof said to the crowd at the Fuerza Patria headquarters, as quoted by Perfil.

Former Peronist president Kirchner, a highly polarising figure in Argentina, received a lifetime ban from politics and a six-year sentence following a lengthy legal process that began with her conviction in December 2022 on charges of fraudulent administration in roadworks contract awards.

"We are in a stage and time where the people and the population are having a very hard time, but allow me to celebrate that with a ballot, we come to put a stop to the government of Javier Milei," Kicillof told the crowd at the Fuerza Patria headquarters, referencing the national government's axing of ARS12bn ($8.8mn) in provincial resources.

The defeat exceeded the margin suggested by pre-election polling, which showed a much closer race. An August survey by consulting firm Analogias shows Peronism's leftist Fuerza Patria leading with 36.9% support compared to La Libertad Avanza's 32.3%.

Milei's performance was further undermined by ongoing corruption allegations surrounding his sister and close advisor Karina, who played a central role in the candidate selection strategy.

This electoral rebuke signals growing resistance to Milei's austerity measures and could complicate his ability to maintain congressional support for his ambitious economic reforms. With markets already under pressure and cracks emerging within the right-wing alliance, the libertarian government faces mounting challenges in sustaining its radical transformation agenda ahead of the more crucial nationwide October mid-term vote.