Assange, who has been holed up in Ecuador's London embassy since 2012, had a personal stake in the race: opposition candidate Guillermo Lasso had threatened to kick him out of the embassy within 30 days if he won the election.
Ecuador decides its future, and maybe Assange's, in runoff
The 45-year-old Australian buoyantly turned that threat around on Lasso as official results showed the conservative ex-banker on track to lose.
"I cordially invite Lasso to leave Ecuador within 30 days (with or without his tax haven millions)," he wrote on Twitter.
That was a reference to WikiLeaks's accusation that Lasso is linked to the Panama Papers tax haven scandal.
"Assange yes, Lasso no," he added in Spanish.
Assange fled to Ecuador's embassy in June 2012 to avoid arrest and extradition to Sweden, where he faces a rape allegation.
The WikiLeaks founder, who denies the allegation, 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.
Outgoing President Rafael Correa, a fiery critic of the US, granted Assange asylum. Moreno, Correa's former vice president, has vowed to uphold it.
Assange accuses CIA of 'devastating incompetence' over leaks
The National Electoral Council said Moreno had 51.07 percent of the vote to 48.93 percent for Lasso, with 94.2 percent of precincts reporting.
But Lasso alleged fraud and said he would contest the result.
COMMENTS
Comments are moderated and generally will be posted if they are on-topic and not abusive.
For more information, please see our Comments FAQ