The son of the late Philippine dictator Ferdinand Marcos was the clear favourite to win Monday's presidential polls when tens of millions of Filipinos cast their vote in the high-stakes elections.

Nearly 40 years after the patriarch was deposed and the family chased into exile, Ferdinand Marcos Junior looks set to complete their remarkable comeback from pariahs to the peak of political power.

Ten candidates are vying to succeed President Rodrigo Duterte in the elections seen by many as a make-or-break moment for Philippine democracy.

The son of the late Philippine dictator Ferdinand Marcos was the clear favourite to win Monday's presidential polls
The son of the late Philippine dictator Ferdinand Marcos was the clear favourite to win Monday's presidential polls AFP / JAM STA ROSA

Relentless whitewashing of the dictator's brutal and corrupt regime, support of rival elite families and public disenchantment with post-Marcos governments have fuelled their revival.

After six years of Duterte's authoritarian rule, rights activists, Catholic church leaders and political analysts fear Marcos Jr will be emboldened to lead with an even heavier fist if he wins by a large margin.

"We think it will worsen the human rights crisis in the country," said Cristina Palabay, secretary general of human rights alliance Karapatan.

The last obstacle to the Marcoses realising their dream of moving back into the presidential palace they occupied for 20 years is Leni Robredo, who narrowly beat Marcos Jr in the 2016 vice presidential race.

The last obstacle to the Marcoses realising their dream of moving back into the presidential palace they occupied for 20 years is Leni Robredo
The last obstacle to the Marcoses realising their dream of moving back into the presidential palace they occupied for 20 years is Leni Robredo AFP / CHAIDEER MAHYUDDIN

Since Robredo announced her bid for the top job in October, volunteer groups have mushroomed across the vast archipelago seeking to convince voters to back what they see as a battle for the country's soul.

Analysts say another Robredo win will be tougher to pull off this time given her huge deficit in the polls, but her millions of diehard fans hold out hope that a late surge in support will be enough to carry her over the line.

While Marcos Jr had a 75 percent chance of winning, the outcome was not guaranteed, said Eurasia Group analyst Peter Mumford, who warned potential complacency among his supporters could work in Robredo's favour at the ballot box.

Ten candidates are vying to succeed President Rodrigo Duterte in the elections seen by many as a make-or-break moment for Philippine democracy
Ten candidates are vying to succeed President Rodrigo Duterte in the elections seen by many as a make-or-break moment for Philippine democracy AFP / CHAIDEER MAHYUDDIN

In the Philippines, the winner only has to get more votes than anyone else.

Around 67 million Filipinos are eligible to vote and turnout is expected to be high when polling stations open at 6:00 am (2200 GMT Sunday).

Tens of millions of Filipinos will cast their votes in presidential polls on Monday
Tens of millions of Filipinos will cast their votes in presidential polls on Monday AFP / CHAIDEER MAHYUDDIN

Robredo, a 57-year-old lawyer and economist, has promised to clean up the dirty style of politics that has long plagued the feudal and corrupt democracy where a handful of surnames hold sway over the country.

Marcos Jr and his running mate Sara Duterte, the daughter of the outgoing president, have insisted they are best qualified to "unify" the country -- though what that means is unclear.

Hundreds of thousands of red-clad supporters turned out at Marcos Jr and Duterte's raucous rally in Manila on Saturday, as they made a last push for votes.

Supporters of Philippines Vice President and presidential candidate Leni Robredo attend a campaign rally in Manila's business district
Supporters of Philippines Vice President and presidential candidate Leni Robredo attend a campaign rally in Manila's business district AFP / MARIA SALVADOR TAN

Josephine Llorca said it was worth betting on another Marcos because successive governments after the 1986 revolution that ousted the family had failed to improve the lives of the poor.

"We tried it and they were even worse than the Marcoses' time," she said.

"We never saw any development. If the other anti-Marcos administrations did well then I don't think we would have any BBM," she said, referring to the scion who is popularly known as "Bongbong".

Surveys indicate Marcos Jr, 64, will win more than half the votes, which would make him the first presidential candidate to secure an absolute majority since his father was overthrown.

Political analyst Richard Heydarian warned such a big win could enable Marcos Jr to make constitutional changes to entrench his power and weaken democracy.

"(Rodrigo) Duterte never had the discipline and wherewithal to push his authoritarian agenda to its logical extreme," Heydarian said.

"That historic opportunity could fall on the lap of the Marcoses."

Other candidates seeking the presidency include boxing legend Manny Pacquiao and former street scavenger turned actor Francisco Domagoso.

But only Marcos Jr and Robredo are seen as having a credible chance of winning.

Marcos Jr went into polling day with a 33 percentage point lead over Robredo, according to the latest Pulse Asia Research survey.

Personality rather than policy typically influences many people's choice of candidate, though vote-buying and intimidation are also perennial problems in Philippine elections.

Allegations of dirty tactics marred the final week of the bitter presidential campaign, as Marcos Jr warned of electoral fraud while Robredo accused him of being a "liar".

In a rousing speech to hundreds of thousands of supporters on Saturday, Robredo declared: "Victory awaits us."

Whatever the result, though, Marcos Jr opponents have already vowed to pursue efforts to have him disqualified over a previous tax conviction and extract billions of dollars in estate taxes from his family.

"It's another crossroads for us," said Judy Taguiwalo, 72, an anti-Marcos activist who was arrested twice and tortured during martial law.

"We need to continue to stand up and struggle."