All three surveys had Economy Minister Sergio Massa in second place and conservative opposition candidate Patricia Bullrich in third.

Two of the polls showed the three candidates within a 10-point range, indicating that a runoff round is likely as none of them may secure the votes to win the poll outright.

To win outright, a candidate needs to secure either 45% of the vote or over 40% with a lead of more than 10 points over their closest rival.

Milei, an economist and political outsider who won a shock victory over establishment heavy-weights at the August primaries with radical proposals, has 34-35% of the vote this month, according to a poll by Opina Argentina. Massa has 29-30% while Bullrich has 24-25%.

A Synopsis Consultores survey showed Milei with 36.5%, followed by Massa with 29.7% and Bullrich with 23.8%.

"The outcome is open," said Opina Argentina analyst Facundo Nejamkis.

Amid an economic crisis that has plunged two in five below the poverty line and seen annual inflation hit 138%, Milei's pledges to dollarize the economy and shut down the central bank have won over some disillusioned voters.

"I voted for Milei in the PASO (primaries) and I am going to vote for him again. It is a change, someone has to remove the Kirchneristas (center-left Peronists)," said Gustavo Machado, a 40-year-old real estate broker from Buenos Aires.

Federico Aurelio, who runs consulting firm Aresco, said: "Milei will reach the runoff unless there is a political earthquake between now and Oct. 22."

He added that Bullrich would have to do "something very special" to overtake Massa.

For some voters, Milei's policies are far too radical.

Nancy Moran, a 58-year-old fruit seller, said she would vote for Massa because under Milei "the peso will disappear."

Most pollsters have not yet released forecasts for a possible Nov. 19 runoff, though Milei is broadly seen as having the best chance of winning.