Argentines are heading to the polls in a general election under the shadow of the South American country’s worst economic crisis in two decades, which has driven the rise of an outsider far-right libertarian who is in pole position to win.

The vote on Sunday is likely to roil Argentina’s already shaky markets, impact its ties with trade partners including China and Brazil, and set the political path for the country, a major grains exporter with huge reserves of lithium and shale gas.

Three frontrunner candidates are likely to split the vote: Libertarian economist Javier Milei, centrist Peronist economy minister Sergio Massa and conservative Patricia Bullrich.

Milei, pledging to “chainsaw” the economic and political status quo, is the candidate to beat, with angry voters flocking to his tear-it-all-down message, fed up with inflation at 138 per cent and poverty affecting over two-fifths of the population.

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“People want things to change,” said Federico Aurelio, president of consulting firm Aresco.

“How? They have no idea, but they want something different.”

Milei, a brash former TV pundit likened to Donald Trump and Jair Bolsonaro, posted a shock win in August open primaries, though Massa and Bullrich were not far behind and it may prove a close race.

Pollsters expect no outright winner.

A candidate needs over 45 per cent of the vote or 40 per cent and a 10-point lead to avoid a second round run-off, which would be held on November 19.

Whoever wins will have to deal with an economy on life support: central bank reserves are empty, recession is expected after a major drought, and a $US44 billion ($70 billion) program with the International Monetary Fund is wobbling.

Amid this crisis Milei has risen abruptly, pledging shock therapy to fix the economy including dollarising, shutting the central bank, reducing the size of government drastically and privatising state entities.

“He is the only one who understands the situation in the country and understands how to save it,” said Buenos Aires student Nicolas Mercado, 22.

Massa, current economy chief, is in the running despite overseeing inflation hitting triple digits for the first time since 1991.

He has pledged to cut the fiscal deficit, stick with the peso and defend the Peronist social welfare safety net.

“Massa represents certain traditional guarantees with which I was raised: public health, state education, which is what I want to defend with my vote,” said astrologer Flavia Vazquez.

Bullrich, a former security minister who is popular in business circles, has seen her support diluted by the unexpected emergence of Milei.

Pollsters see her as the most likely of the top three runners to miss out on a second round.

-Reuters