The results are in line with opinion polls that had predicted the low-key reformist was heading for a second five-year term
Private pollsters data based on a partial count of samples from polling stations showed that Widodo was winning more than half of the vote and his challenger, former general Prabowo Subianto, was more than 10 percentage points behind him.
One of the pollsters, the Jakarta-based CSIS, showed Widodo with 56.7% and Prabowo at 43.3%, after just over half of the votes were counted.
“We are not claiming anything yet,” CSIS Executive Director Philips Vermonte told Reuters. “The data will likely stabilise at 90%. Our staff are validating the data.”
Asked to comment on the “quick count” results, Prabowo campaign spokesman Dahnil Anzar Simanjuntak said that numbers based on 50% of votes was not enough.
“We will wait,” he said.
The one-day elections for both the presidency and legislature seats followed a campaign across the sprawling equatorial archipelago that was dominated by economic issues but was also marked by the growing influence of conservative Islam.
The eight-hour vote across a country that stretches more than 5,000 km (3,000 miles) from its western to eastern tips was both a Herculean logistical feat and testimony to the resilience of democracy two decades after authoritarianism was defeated.
Widodo, a furniture businessman who entered politics 14 years ago as a small-city mayor, narrowly defeated Prabowo in the last election, in 2014.
A senior government official close to the president said before the election that a win for Widodo with 52-55% of the vote would be a “sweet spot”, and enough of a mandate to press on with, and even accelerate, reforms.
The winner may be known by late on Wednesday, though official results will not come until May. Any disputes can be taken to the Constitutional Court where a nine-judge panel will have 14 days to rule on them.
More than 10,000 volunteers crowd-sourced results posted at polling stations in a real-time bid to thwart attempts at fraud.
However, even before the election, the opposition alleged voter-list irregularities that it said could affect millions and vowed legal or “people power” action if its concerns were ignored.
Widodo campaigned on his record of deregulation and improving infrastructure, calling his first term a step to tackling inequality and poverty in Southeast Asia’s biggest economy.
Bread-and-butter issues were at the forefront of the minds of many voters.
“I hope in future prices of staple foods will be cheaper, especially as we are heading into Ramadan and Eid al-Fitr,” said Nurani, a 41-year-old mother of three, voting in Bandar Lampung in Sumatra.
But religion was also a factor in the election in the world’s most populous Muslim-majority country, where conservatives have been increasingly influential.
Widodo, a moderate Muslim from Java island, had to burnish his Islamic credentials after smear campaigns and hoax stories accused him of being anti-Islam, a communist or too close to China, all politically damaging in Indonesia. He picked Islamic cleric Ma’ruf Amin, 76, as his running mate.
Prabowo, a former special forces commander who has links to some hardline Islamist groups, and his running mate, business entrepreneur Sandiaga Uno, pledged to boost the economy by slashing taxes and cutting food prices.
(Additional reporting by Maikel Jefriando, Tabita Diela, Kanupriya Kapoor, Cindy Silviana in Jakarta, Tommy Ardiansyah in Bogor, Mas Alina Arifin in Bandar Lampung; Writing by John Chalmers and Ed Davies)