Lenín Moreno, a 64-year-old former vice president of Ecuador, appeared headed to a second-round win in the country’s presidential election on Sunday. It would be a rare victory for the Latin American left, which has recently suffered stinging election defeats.
With more than 90 percent of the votes counted, Mr. Moreno, a close ally of departing President Rafael Correa, had won 51 percent of the vote, while his opponent, Guillermo Lasso, a 61-year-old banker, had won 49 percent, according to early figures published by Ecuador’s electoral commission.
While Mr. Moreno quickly declared victory on Sunday night, his opponent did not concede, saying all the votes needed to be counted.
The race was closely watched in the region, where, time and again, leftist stalwarts who rose to power on populism and high commodity prices have seen their fortunes turn.
Liberal movements in Venezuela, Argentina and Bolivia have been rebuffed by voters in recent elections as their economies have stumbled. Brazil’s leftist president, Dilma Rousseff, was brought down by impeachment last year.
In the end, it was the candidate named for the founder of Russian Communism who was favored to win.
Mr. Moreno has promised to push forward the so-called Citizens’ Revolution of his predecessor, which funneled state funds back to the poor in the form of education, housing and infrastructure.
In a speech on Sunday, Mr. Moreno said it became clear during his travels that he had the support of ordinary Ecuadoreans. “Since before we claimed victory, we knew it, we felt it,” he said.
Yet maintaining Mr. Correa’s momentum could prove hard. There is the issue of oil revenues, for one, which have stagnated. The economy has ground to a halt after years of high growth.
There is also the figure of Mr. Correa himself, a strong-willed populist who ruled for a decade, created a new Constitution and lifted large sections of his nation out of poverty. Few expect that the mild-mannered Mr. Moreno can sustain his success.
“The economic orientation will change; the social emphasis will change,” said Simón Pachano, a political analyst based in Quito, the capital.
Still, Mr. Moreno’s vision differed sharply from that of his opponent, Mr. Lasso, who lost to Mr. Correa by a larger margin in 2013.
Mr. Lasso, from the port city of Guayaquil, had promised to cut back on what he called the excesses of the previous president, including by reducing the public-sector work force and government spending. He also proposed cutting taxes for the wealthy and for businesses.
Each candidate faced a steep climb to the presidency. Mr. Moreno was criticized for being too close to Mr. Correa, whose decade in power ended with accusations of corruption involving public infrastructure projects. Mr. Correa earned a harsh reputation for attacking critics, suing journalists and, on his state television show, angrily reading the names of those who had sent tweets that reflected poorly on him.
But for many, Mr. Lasso was never able to overcome his history as banker in a country that has been rocked by financial crises and inflation.
His opponents hammered him throughout the campaign for his past positions in the government of Jamil Mahuad, the Ecuadorean president who moved the country onto the United States dollar after a banking crisis destroyed its national currency, the sucre.
The financial collapse, known as the “bank holiday” in Ecuador, prompted a migration of more than 1.5 million people, most of whom sought work in the United States and Europe. The country limped by in negotiations with creditors for years until Mr. Correa took Ecuador into default, calling the foreign debt “immoral.”
More recently, an Argentine newspaper published what it said were documents showing that Mr. Lasso had shuttled financial gains he made during the country’s economic crisis into an offshore account. Mr. Lasso denied wrongdoing, but Mr. Correa said the candidate was under investigation.
Mr. Moreno, by contrast, presented a softer image.
Known to be more humorous and conciliatory than Mr. Correa, he appeared in campaign stops in his wheelchair, which he has used since he was shot during a robbery in the late 1990s. He is probably best known for his social programs, which have helped people with disabilities in Ecuador.
“We can’t lose what’s been given to the poor,” said Edwin Tatés, who works as a driver in Quito and voted for Mr. Moreno.
He added, “This government has had many errors, above all those of Correa, who has fought with everyone, but we need to change things for the good of the country, not to change the whole government.”