Rene Preval had 50.3% of the vote so far with over half the votes counted, barely above the 50% plus one vote threshold needed to avoid a run-off on 19 March.
On Thursday, early results appeared to indicate that Preval was on course for an outright victory after he won 61.5% of the first 15% of a predicted 1.75 million votes.
Another former president, Leslie Manigat, was in second place with 11.4% and industrialist Charles Baker held third with 8.3%, according to the results published by the Provisional Electoral Council.
Champion of the poor
Preval was president of the impoverished Caribbean nation between 1996 and 2001 and is an ally of Jean-Bertrand Aristide who was overthrown as leader two years ago, prompting the political instability and gang violence that has plagued the country.
Preval inherited much of Aristide's support in the slums of the capital Port-au-Prince and is the favoured candidate of Haiti's poor.
If he does win, he will have to immediately begin negotiating with opposition parties in parliament, where his Lespwa Party is expected to be weak, to select a prime minister. And he must stem gang violence that is driving out manufacturers and eliminating thousands of jobs.
Large numbers of voters turned
out for the elections
"Everything in Haiti is broken and everything needs fixing," according to Robert Maguire, director of the international affairs programme at Trinity University in Washington.
"One of the most immediate tasks is reconciliation and dialogue among Haitians," he said.
A Preval presidency could, on the other hand, prove unsettling to the United States, which pushed towards removing Aristide from power two years ago.
On Friday, Washington urged Preval, who was keeping a low profile in his hometown of Marmelade in the north, to oppose Aristide's return from exile in South Africa.
Aristide, a former priest, was accused of despotism before being driven from power.
Although he has distanced himself from his mentor, Preval has not said that he will block Aristide's return to the country.
Meanwhile Charles Baker, who was lying in third place in the voting and is the preferred candidate of Haiti's wealthy elite, confirmed on Friday that he has asked for an investigation into possible fraud.
Baker said he had asked election officials to investigate whether people were allowed to vote more than once because voter lists were not followed. "We had a lot of (polling station) volunteers who said they saw people voting five times, seven times, eight times," he said.International observers have said they saw some irregularities at polling stations but have not suggested the results were tainted by fraud. A significant percentage of ballots cast have been nullified.