Robredo has pledged to increase investment to tackle climate change, level the playing field for business, and promote public-private partnerships.
Marcos, 64, has not presented many details about his policies but is expected to carry ahead with the same approach as his predecessor Duterte, pursuing a ruthless consolidation of power.
Critics say Marcos is attempting to rewrite the family's controversial history for a youthful electorate, though they believe he is unlikely to replicate his father's authoritarian style of ruling.
Duterte's daughter, southern Davao city Mayor Sara Duterte-Caprio, has topped surveys as Marcos Jr.'s vice-presidential running mate.
What's at stake?
"History may repeat itself if they win. There may be a repeat of martial law and the drug killings that happened under their parents," human rights worker Myles Sanchez told AP news agency regarding a Marcos Jr./Duterte-Caprio victory.
Also read: Philippines, US Hold Biggest Military Exercises in Seven Years
Robredo, 57, is a former human rights lawyer and staunch liberal and has pledged to improve education and welfare, fight poverty and improve market competition if elected. She had narrowly defeated Marcos in the run for the vice presidency in 2016.
She has criticized Duterte's war on drugs, and condemned the "senseless killings."
A win for Robredo would make her the third woman to lead the Philippines after democracy champion Corazon Aquino in 1986 and Gloria Macapagal-Arroyo in 2001.
She is running with Francis Pangilinan, a lawyer, and senator, and the latest survey put her in second place, with 23 percent support.
Source: AFP, AP, Reuters
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