Quito: Ecuador votes on Sunday in a presidential runoff to turn the page on a decade under radical economist Rafael Correa and decide whether the country will follow Latin America's recent shift to the right.

The election could also decide the fate of WikiLeaks founder Julian Assange, who has been holed up at the country's London embassy since 2012.

Correa presided over an economic boom that has recently gone bust in the South American oil producer. With voters torn between continuity and change, the race remains too close to call.

The runoff pits the socialist president's designated heir, Lenin Moreno, against conservative ex-banker Guillermo Lasso.

Lasso finished second in the first-round vote last month, with 28 per cent to Moreno's 39 per cent. But polls give him a slight edge heading into the runoff, with between 52.1 per cent and 57.6 per cent of the vote.

The race is also a barometer of the political climate in Latin America, where more than a decade of leftist dominance has been waning.

Argentina, Brazil and Peru have all shifted to the right in recent months, as the region has sunk into recession and leftist leaders have been tarnished by a string of corruption scandals.

Boosted by high prices for its oil exports, Ecuador registered solid economic growth of 4.4 per cent per year on average during the first eight years of Correa's presidency, before tipping into recession in mid-2015.

Correa won loyal fans among the poor with generous social benefits that helped reduce the poverty rate from 36.7 per cent to 23.3 per cent in this country of 16 million people.

But he has also faced accusations of corruption and squandering the windfall of the oil boom.

Political analyst Napoleon Saltos of the Central University of Ecuador said the election would be played out between "the vote against the government and the fear among certain parts of the population that they will lose what they gained over the past 10 years."

Lasso, 61, appears to have gained the edge by uniting the opposition vote behind his promises to end tax-and-spend policies and create a million jobs.

But Moreno, 64, has sought to co-opt the buzzword of "change" for himself.

"We're heading for a change, yes, but a positive change not a negative change, a change toward the past," he told AFP on Wednesday.

In another of the race's hot debates, Lasso has threatened to revoke the political asylum Ecuador has granted its most famous guest, Assange.

Correa, an outspoken critic of the United States, let Assange stay at the embassy to avoid arrest and extradition to Sweden over a rape allegation.

The 45-year-old Australian, who denies the accusation, says he fears Sweden would send him to the United States to face trial for leaking hundreds of thousands of secret US military and diplomatic documents in 2010.

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