Image copyright Facebook Image caption Jose Antonio Castro is leading in early results
The Honduran left is poised to take power in the Central American country after a historic first-round election.
Jose Antonio Castro has been leading his closest rival Carlos Lopez by more than 50% of the vote.
Ms Lopez is the sister of Honduras’ outgoing president, Mr Lopez’s mentor Ricardo Maduro.
The results of the first-round were due to be announced on Sunday, with a runoff final on 17 June.
Their main opponents are Prime Minister Juan Orlando Hernandez and Liberal Party candidate Mauricio Villeda.
Image copyright CNN Image caption Mr Maduro and Mr Lopez’s father were close political allies
Political analysts have expressed surprise at Mr Lopez’s lead.
In the first-round presidential election last month, Mr Hernandez won by more than 30 percentage points, but he fell just short of the 50% that would have triggered a run-off against Mr Villeda.
Mr Hernandez’s government is accused of attempting to suppress genuine political opposition.
The government is also widely blamed for fostering poverty and widespread violence in the country of eight million people.