Argentina’s governing libertarian coalition, La Libertad Avanza, has formalised an electoral alliance with Propuesta Republicana, the party founded by former president Mauricio Macri, for the 7 September legislative elections in Buenos Aires Province. The accord was announced in Buenos Aires by Karina Milei, secretary-general of the Presidency, together with Sebastián Pareja, LLA’s provincial organiser, and senior PRO lawmakers Cristian Ritondo and Diego Santilli. Pareja said the joint front will be registered as “Alianza La Libertad Avanza”, reflecting the predominance of the libertarian brand, while PRO confirmed that its 13 mayors in the province will join the ticket. Karina Milei praised PRO for “setting aside particular interests to confront kirchnerismo,” the Peronist faction led provincially by Governor Axel Kicillof. The deal alters the balance of power in Argentina’s most populous district, long considered a Peronist stronghold. In response, Kicillof, provincial party chairman Máximo Kirchner and former economy minister Sergio Massa reached a late-night agreement to field a single Peronist slate, with a unified electoral board representing their three factions. Candidate lists for the 7 September vote must be filed by 19 July. Buenos Aires Province, home to more than 17 million people, elects the largest bloc of national deputies, making the provincial outcome critical for President Milei’s legislative agenda.