Mauricio Macri's running mate in the October presidential race could be a deciding factor if the president hopes to get over line against a Peronist contender, with the head of state's poll numbers showing no immediate signs of improvement.
The issue has boiled over into an acutely political one this week, as members of the UCR Radical Party, a coalition ally of Macri's, began urging for the candidacy to be ceded to a Radical.
Some UCR party members, particularly in Córdoba province, have shown signs that they are willing to split from the coalition if it means winning local and provincial races in their heartland.
Macri was due to meet Radical leaders next Monday but the meeting has been postponed due to "scheduling issues," UCR president Alfredo Cornejo told Radio La Red on Wednesday.
He reported that Macri's Cabinet Chief Marcos Peña and Jujuy province's Governor Gerardo Morales, a Radical, had progressed in their discussions "not only about the idea of being part of the [presidential] formula but also to look over where we've come from" in terms of coalition unity.
"This is not a rumour. There is a concrete chance that a Radical will accompany Macri" on the presidential ticket, he added.
Interior Minister Rogelio Frigerio told reporters that the government was "open" to considering a Radical for the vice-presidential post.
Other UCR party members and dissident Radicals have pressured the government to open top government and legislative spots up to a primaries race where all coalition members can compete.
"There shouldn't be any fear about competing in a primaries race. It's strange that someone would suggest that winning depends on them not being challenged, right?", said coalition member Martín Lousteau in an interview with La Nación.
Lousteau, along with former lawmaker Ricardo Alfonsin, are two of the major "radical" proponents of change within the coalition.
With clouds of tension building over the Cambiemos (Let's Change) alliance, some observers say the coalition's dominant party, President Macri's PRO, would be wise to cede the spot to a candidate from the UCR Radical Party. However, only PRO party names have dominated rumours, with names like Security Minister Patricia Bullrich and Health and Social Development Minister Carolina Stanley appearing as frontrunners.
"The president has not offered me anything. It's an issue that will be decided upon intimately. The area he gave me is one which people recognise because of changes to laws and the defence of victims," Bullrich said recently, speaking to the A24 news channel.
The running-mate position should be given to a woman, according to Macri's political guru Jaime Durán Barba. Bullrich and Stanley are two of the names being heavily considered, Perfil reported l;ast weekend.
Meanwhile, sources close the president told La Nación this week that current vice-president, Gabriela Michetti, remains the head of state's preferred choice.
Michetti enjoys a positive public image and has won every election she has contended: as Macri's deputy mayor running-mate in the City of Buenos Aires, the 2009 mid-terms as the lead PRO Party candidate for the Lower House, and in the 2013 mid-terms as a Cambiemos (Let's Change) senator. Her only loss was against current BA City Mayor Horacio Rodríguez Larreta in a primaries race in 2015, in which Macri and his Cabinet Chief Marcos Peña openly threw their weight behind Rodríguez Larreta.
Other names reportedly being tested, both publicly and privately, include Peña, Frigerio and Transport Secretary Guillermo Dietrich. In the event any one of these men were chosen, it would be the first time in the history of Macri's political career that he has run alongside a male running-mate.