Rafael Correa has pulled ahead in a poll, a day before Ecuadorean voters decide whether he or Alvaro Noboa, a banana mogul, will be the country's next president.
Saturday's poll showed Correa, a former finance minister allied with Hugo Chavez, Venezuela's president, ahead of Noboa by eight percentage points before Sunday's run-off election.
The Cedatos-Gallup poll showed support for Correa increasing to 54 per cent while backing for Noboa slipped to 46 per cent.
The survey of 5,658 people was taken on Friday and has a three percentage point margin of error.
Both candidates have promised to create jobs and fight corruption.
About 17 per cent of Ecuadoreans were still unsure about their mandatory vote as they decide who of the two candidates offers the best remedies to the political turmoil that has forced out three presidents in 10 years in the poor Andean country.
Marta Zabala, a pregnant housewife in the impoverished August 28 barrio outside Guayaquil city, said: "I'm not sure who. If either does anything for the country it will be a surprise. They forget about places like this. For me, it will probably be Alvaro."
Noboa, 56, who is Ecuador's wealthiest man, won an October first-round vote with a populist campaign offering jobs and cheap housing.
The stark contrast between the two candidates reflects a broader split in South America, where Chavez has drawn support with his message of socialist revolution to counter US influence and free-trade policies.
Correa spooked Wall Street and centrist voters with promises to overhaul congress and renegotiate foreign debt, but he has gained momentum after softening his tone.
Electoral authorities said they expect initial results as early as Monday morning, but the very tight race and Correa's charges of possible vote rigging have raised concerns of possible post-election protests.
Both men come from the port city of Guayaquil, where coastal areas live off tuna and shrimping and rural roads are lined with the banana plantations that make Ecuador the world's top exporter of the fruit.