JAKARTA (Reuters) - Indonesians vote in the world’s biggest single-day election on Wednesday, with polling stations opening first in the east of the sprawling equatorial archipelago after a six-month campaign to choose a new president and parliament.

A supporter covers his head with a T-shirt with the image of Indonesia's incumbent presidential candidate Joko Widodo during a campaign rally at Gelora Bung Karno stadium in Jakarta, Indonesia, April 13, 2019. REUTERS/Willy Kurniawan

President Joko Widodo, a furniture businessman who entered politics 14 years ago as a small-city mayor, is seeking re-election against former general Prabowo Subianto, whom he narrowly defeated in the last election, in 2014.

The economy has dominated a hard-fought campaign, though the rise of political Islam has loomed over the vote in the world’s most populous Muslim-majority country.

Most opinion polls give Widodo a double-digit lead but the opposition says the race is much closer. It alleges data irregularities that could affect millions of voters and has vowed legal or “people power” action if its concerns are ignored.

“The system is not foolproof, but there are enough checks and balances in place,” Kevin O’Rourke, a political analyst and author of the newsletter Reformasi Weekly, said this week.

He said problems with voter lists “are not so bad that it can affect the outcome of the election”.

An unexpected win for the challenger could trigger a brief selloff in financial markets that have priced in a Widodo victory, analysts say.

“Should Prabowo win, this would literally be the end of opinion polling in Indonesia ... and a major, major upset,” said Marcus Mietzner, associate professor at Australian National University.

“The question is what the margin of victory will be,” he said, predicting Widodo’s re-election.

Graphic: Presidenti Joko Widodo's achievements - tmsnrt.rs/2CRgHYC

‘GAME OF THRONES’

Slideshow ( 2 images )

Poll-related hashtags were trending on Twitter in Indonesia during a three-day quiet period in the run-up to voting day.

Social media users compared the presidential race to the HBO series “Game of Thrones” - with one online meme showing Widodo sitting on its coveted Iron Throne.

Widodo has touted his record on deregulation and improving infrastructure, calling it a first step to tackling inequality and poverty in Southeast Asia’s biggest economy.

A moderate Muslim from central Java, Widodo has 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 has 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, say they will boost the economy by slashing taxes and focusing on infrastructure.

QUICK COUNTS

Nearly 350,000 police and soldiers will join 1.6 million paramilitary officers stationed across the country of 17,000 islands to safeguard the vote.

More than 192 million people are eligible to cast ballots in national and regional legislative elections being contested by more than 245,000 candidates.

Polling stations will open at 7 a.m. (2200 GMT on Tuesday) in the east and close at 1 p.m. (0600 GMT) in the west.

Voters will have five paper ballots for president, vice president, and national and regional legislative candidates.

Unofficial “quick counts”, based on samples from polling stations, will be released hours after voting ends. The winning presidential candidate could be known by late Wednesday.

Official results will be announced in May. Any disputes can be taken to the Constitutional Court where a nine-judge panel will have 14 days to rule on them.