Arman Maulana told the Sydney Morning Herald and The Age that in 2014, when Joko beat Prabowo by 6.3 percentage points, he had voted for Prabowo. This time, he had changed his vote.

"I voted for the 'calm' one. I used to be Prabowo's supporter, a big supporter ... I changed to Jokowi [the president's popular nickname] because after he was president, my kids can go to school and the most important thing is healthcare, we don't have to pay anything now if we are sick.

"For us, the orang kecil [little people], before, if you don't have money [for a doctor] you're pretty much dead," he said.

"Jokowi is adem [cool or calm], just look at him during the debates, he never attacked anyone, unlike Prabowo. Jokowi would also accept if he was defeated. Prabowo will protest, he will fight, he just wants to win."

But 21-year-old Sarah, a first-time voter who works for a convenience store chain, said she had voted for Prabowo because the economy was her primary concern.

"The economy is [the most important issue]. I want it to be improved and I hope there will be no corruption anymore," she said.

Prabowo has frequently criticised Joko's focus on infrastructure, which has seen thousands of kilometres of roads, rail and new air and sea ports built, along with an underground train in Jakarta. He has also frequently argued that Indonesia's economy has grown weaker under the current president, even as the cost of basic staples has grown and corruption has worsened.

Ida, 42, said she had also voted for Prabowo because food and electricity had grown too expensive.

She dismissed Jakarta's new toll roads as "only for people who can afford to pay for it" and added that "we need cheaper prices here".

But in a middle class area of Bekasi, a satellite city on the eastern outskirts or Jakarta, 21-year-old psychology student Putri Elma said she had voted for Joko because of his huge building program and improved healthcare.

"My views are different to Prabowo's. He complains about the elite but himself is the elite. He says he wants to raise the salary of the civil servants so that they won't do corruption, in fact it is the elite or the rich who are corrupt. He's also a short-tempered man," she said.

In Grogol south, in south Jakarta - an area in which large houses sit across the street from far humbler ones - wealthier, ethnically Chinese Indonesian voters uniformly said they would support Joko, who is seen as the more inclusive candidate.

One older Chinese-Indonesian voter, who asked not to be named, said the events of 1998 remained pertinent. Then, the former dictator Suharto (Prabowo's former father-in-law) lost power and Prabowo himself was accused of using civil militias to stoke anti-Chinese riots (a charge he has always denied).

Heny Purwanti Sari Liadi said this was her second time voting and that she had once again backed Joko.

"I think five years is not enough for the president to change the nation, I think in another five years we can see how he has changed Indonesia," she said.

"I think infrastructure [has been good]. Transportation, like the MRT in Jakarta, the Asian games, I think it is another step towards Indonesian being a better country."

Opinion polls have for months given Joko a strong lead over Prabowo, in some cases as much as 20 percentage points, but on the eve of the vote Prabowo predicted he would win by a big margin.

Political analysts believe that while Joko is in the box seat, the result will be much closer than the polls predict.

Prabowo has flagged a challenge in the Constitutional Court and street protests if he loses.

After voting, Prabowo said "I promised that we will work for the good of the country. If it's chaos or not it's not coming from us, but I guarantee that we don't want to be cheated anymore, that Indonesian people don't want to be cheated anymore."

Joko said after voting that he was feeling optimistic about the results of Wednesday's poll.

Unofficial results from so-called "quick counts" - which are usually accurate to within a couple of percentage points - are expected late Wednesday afternoon or early evening, Jakarta time.

In addition to the presidential vote, there are 20,000 local and national seats up for grabs, more than 245,000 candidates running, more than 800,000 polling booths and more than 6 million election workers in what is, by some measures, the world's largest single-day election.