MANILA (UPDATE)—Sen. Christopher Lawrence Go on Saturday filed his certificate of candidacy (COC) for vice president in the May 9, 2022 elections, after initially rejecting calls to attempt to succeed President Rodrigo Duterte.

Go registered his candidacy past 3 p.m. Saturday, accompanied by Duterte, whose subsequent announcement that he was not seeking a position in next year's elections highlighted Day 2 of the COC filing.

In a statement, Go said he will run for vice president after Duterte withdrew his acceptance of the PDP-Laban nomination for the same post. This was not made public until Go's filing.

"Given that President Rodrigo Duterte decided to withdraw his acceptance of nomination, I am here to take on the challenge as PDP-Laban’s Vice Presidential candidate," Go said in a statement.

He vowed to continue Duterte's flagship programs, particularly the controversial anti-drug campaign and the completion of Build, Build, Build projects.

Go, who also promised to fight poverty through his Malasakit Centers, is Duterte's long-time aide, widely seen as the gatekeeper to the president and still attending to the chief executive's needs even after his election to the Senate.

He was assistant to Duterte when he was a congressman and is almost always by his side at public events and at Malacañang.

The chairman of the Senate committees on health and sports, Go also frequently posts "selfies" with Duterte on social media.

When he announced his candidacy on Saturday, Go promised to be a "working vice president", not a token official.

"Hindi ako magiging spare tire o reserba lamang. Asahan ninyo na ako ay totoong magtatrabaho. Hindi lang sa salita, kundi sa gawa," he said.

"I don’t want to be remembered as just another senator or vice president. I want to be remembered as a public servant na nalalapitan ng sinumang ordinaryong mamamayan at buong pusong nagsisilbi para sa ikabubuti ng ating bansa."

Last month, Go had declined his party's presidential nomination, despite Duterte urging him to pursue. The senator said his "heart and mind are focused on serving people."

But Go, 47, also said he was leaving his fate to God, the Dutertes, and the public.

Duterte earlier accepted his nomination for vice president as Go's running mate.

Experts believe Duterte, a maverick leader famous for his embrace of China and disdain for ally the United States, could be making a play for retaining power by taking over as president under a scenario in which his successor resigns.

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Critics are convinced Duterte has ambitions to retain power, or remain in high office to stymie possible legal action over thousands of state killings during his notorious war on drugs.

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But Duterte said he wants to serve the public.

A recent survey by Social Weather Stations showed 60 percent of 1,200 respondents believe his move violates the intention of the constitution, which has a 1-term limit to prevent abuse of power.

A separate poll by Pulse Asia showed Senate President Vicente Sotto III overtaking Duterte as the most preferred prospect for vice president.

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The President's daughter, Davao City Mayor Sara Duterte-Carpio, has topped surveys for the top job, outshining Go.

But she said she would not seek higher office because of her father's vice presidential bid.

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Political analysts say Duterte-Carpio might still make a last-minute bid for the presidency, as her father did in 2015. The Commission on Elections allows substitutions until November 15.

— With reports from Jamaine Punzalan and Jauhn Etienne Villaruel, ABS-CBN News; Reuters