Sergio Massa will head the list of Lower House candidates representing the Frente de Todos (Front for All) alliance in the October general elections, the candidate confirmed Tuesday.
Massa last week confirmed he was abandoning the dissident Peronist alliance known as Alternativa Federal to join his former foe Cristina Fernández de Kirchner's Unidad Ciudadana (Citizens United) movement in Frente de Todos.
He will lead the coalition's list of candidates representing Buenos Aires province, the country's largest by population.
"We have made the decision to lead the list of lawmaker for Buenos Aires", Massa said at a panel event organised by the Clarín media group on Tuesday at the Latin-American Art Museum of Buenos Aires (MALBA).
Massa's manoeuvring reflects the Motley Crew-like nature of Peronism. His decision surprised many, since it is far from the presidential ambitions the former Cabinet Chief and ANSES welfare bureau chief had expressed until as recently as last week when he remained a lead "third option" candidate for the presidency, opposing both President Mauricio Macri and former president Fernández de Kirchner.
He insisted that his ambitions to one day become president were firm.
"I had, have and am going to always have the desire to be the president of Argentina", he insisted.
Justifying his decision to join an alliance that is pushing his predecessor as Cabinet chief Alberto Fernández's candidacy for president, alongside Fernández de Kirchner as vice-presidential candidate, Massa insisted the time was not right for him.
"It's a time in which one must have a sense of humility and recognise the limits on his ability to fight in the time and place", he said.
"I feel like our responsibility today should be placed in constructing a large opposition force. Beyond my personal interest, we must give Argentinas this new majority in order to have a new government", the former mayor of Tigre province added.
Massa's decision to join Frente de Todos comes amid a wave of Peronist wins in provincial elections, including Santa Fe province where Peronists return to power after 12 years in opposition.
His former colleague Graciela Camaño - considered Massa's "political mother" - refused to join Massa in the new alliance. Rumours suggest she will run as a candidate for Governor of Buenos Aires province, supporting former Economy minister Roberto Lavagna's presidential nomination.