BUENOS AIRES, Argentina (AP) — Argentine President Javier Milei suffered a sweeping setback on Sunday in a Buenos Aires provincial election widely viewed as a political test for his libertarian party and a barometer for its performance in the important congressional midterms next month.

Milei's recently formed La Libertad Avanza party captured just 34% of the vote in Argentina’s biggest province, losing by a landslide to the left-leaning Peronists, which secured 47% of the votes.

Milei conceded that his party’s loss represented “a clear defeat.” He told gloomy supporters at his party headquarters, “If we’ve made political mistakes, we’re going to internalize them, we’re going to process them, we’re going to modify our actions.” Despite the defeat, Milei vowed to stick with his sweeping economic overhaul, insisting there would be no retreat in government policy.

As he grapples with a struggling economy and a corruption scandal involving close associates, Milei's party faces increased scrutiny ahead of the midterms. Analysts had anticipated that his party would face challenges, but the extent of the loss is seen as a severe blow to his agenda.

Peronist leader Cristina Fernández de Kirchner, currently under house arrest following a corruption conviction, took to social media celebrating the victory, further complicating Milei's position as he seeks to strengthen his party’s influence within a deeply divided congress.

As the stakes rise for the upcoming midterms, the election results indicate a shifting political landscape in Argentina, with potential implications for investor confidence and international relations.