After months of behind-the-scenes negotiations, a deadline for candidates closes on Saturday night, marking the serious start of a race towards Oct. 22 general elections to choose a leader who can steer the South American country out of economic crisis, with inflation over 100%, rising poverty and dwindling foreign currency reserves.

There will be a primary vote on Aug. 13 within political blocs, a ballot which will also be a key litmus test of voter sentiment, with the ruling Peronist alliance reeling in opinion polls as the embattled economy struggles.

The most notable late confirmation has been Economy Minister Sergio Massa, whose candidacy was announced somewhat unexpectedly Friday night.

"This completely changes the political scene," said Alejandro Corbacho, director of political science program at Argentine University UCEMA. "He has the support of important business sectors here and he's going to be a competitive candidate."

The ruling party announced Massa and chief of staff Agustin Rossi as the unified coalition ticket just a day after interior minister Eduardo 'Wado' de Pedro announced his candidacy and ambassador to Brazil Daniel Scioli reaffirmed his decision to run. Neither has publicly ended his candidacy. Both were polling behind Massa.

Competing to lead the main conservative opposition bloc - which tops overall polls - are moderate Buenos Aires city mayor Horacio Larreta and more hard-line ex-security minister Patricia Bullrich. Behind them is centrist congressman Facundo Manes.

Bullrich, who touted party unity at a Friday press conference and later blamed Massa for the country's economic issues, pledged wholesale change if she won.

"This ticket is committed to deep change," she said. "Argentina needs leaders with conviction because the problems to solve are deep."

Posting a stern challenge to them all is libertarian economist Javier Milei, the most popular single candidate in polls with many voters fed up with the political status quo. His party overall, though, still sits in third place. He has pledged to dollarize the economy and scrap the central bank.

"He complicates the life of the other two coalitions because he will take votes away from them," said Argentine political consultant Carlos Fara, adding that his personal charisma might however be tempered by his more limited party structure.

Larreta, Bullrich, and Massa are roughly even in the polls, with Milei polling slightly ahead. With no candidate or party polling over 50%, the likelihood is the October election will lead to a run-off, with all still to play for.