Voters in Argentina have cast ballots in a presidential run-off election that will determine whether South America’s second-largest economy will take a rightward shift.

Populist Javier Milei, an upstart candidate who got his start as a TV talking head, has frequently been compared to former US president Donald Trump.

He faces economy minister Sergio Massa of the Peronist party, which has been a leading force in Argentine politics for decades.

On Mr Massa’s watch, inflation has soared to more than 140% and poverty has increased. Mr Milei, a self-described anarcho-capitalist, proposes to slash the size of the state and rein in inflation, while Mr Massa has warned people about the negative impacts of such policies.

The highly polarising election is forcing many to decide which of the two they consider to be the least bad option.

Voting stations opened at 8am local time and close 10 hours later. Voting is conducted with paper ballots, making the count unpredictable, but initial results were expected around three hours after polls close.

Mr Milei went from blasting the country’s “political caste” on TV to winning a political seat two years ago.

The economist’s screeds resonated widely with Argentines angered by their struggle to make ends meet, particularly young men.

“Money covers less and less each day. I’m a qualified individual, and my salary isn’t enough for anything,” Esteban Medina, a 26-year-old physical therapist from Ezeiza, on the outskirts of Buenos Aires, told The Associated Press on the sidelines of a Milei rally earlier this week.

Mr Massa, as one of the most prominent figures in a deeply unpopular administration, was once seen as having little chance of victory.

But he managed to mobilise the networks of his Peronist party and clinched a decisive first-place finish in the first round of voting.

His campaign has cautioned Argentines that his libertarian opponent’s plan to eliminate key ministries and otherwise sharply curtail the state would threaten public services, including health and education, and welfare programmes many rely on.

Mr Massa has also drawn attention to his opponent’s often aggressive rhetoric and has openly questioned his mental acuity; ahead of the first round, Mr Milei sometimes carried a revving chainsaw at rallies.

Mr Milei has accused Mr Massa and his allies of running a “campaign of fear” and he has walked back some of his most controversial proposals, such as loosening gun control.

In his final campaign ad, Mr Milei looks at the camera and assures voters he has no plans to privatise education or health care.

Most pre-election polls, which have been notoriously wrong at every step of this year’s campaign, show a statistical tie between the two candidates.

Voters for first-round candidates who did not make the run-off will be key. Patricia Bullrich, who placed third, has endorsed Mr Milei.

The vote takes place amid Mr Milei’s allegations of possible electoral fraud, reminiscent of those from Mr Trump and former Brazilian president Jair Bolsonaro.

Without providing evidence, Mr Milei claimed that the first round of the presidential election was plagued by irregularities that affected the result.

Experts say such irregularities cannot swing an election, and that his assertions are partly aimed at firing up his base and motivating his supporters to become monitors of voting stations.

Such claims spread widely on social media and, at Mr Milei’s rally in Ezeiza earlier this week, all those interviewed told the AP they were concerned about the integrity of the vote.