MANILA - Philippine politics has taken a bizarre turn, with the prospect of President Rodrigo Duterte running against his own daughter for the vice-presidency in elections next year.

Ms Sara Duterte-Carpio, 43, on Saturday (Nov 13) filed the papers necessary to make her run for office official.

She is entering the race by way of substitution, replacing the candidate for vice-president of Lakas (Strength), the political party of former president Gloria Arroyo that she joined only on Thursday.

But then, just hours later, her 76-year-old father showed up at the head office of the poll commission in Manila to accompany his long-time aide, Senator Bong Go, who withdrew his candidacy for the vice-presidency to run for president instead.

Mr Duterte's press secretary, Mr Martin Andanar, then announced that the President would return to the commission's office on Monday to formalise his own bid to run for vice-president, under Mr Go, just over a month after announcing that he was retiring from politics.

Mr Go was less forthright.

"I can answer only for myself. Let's just wait for the President's decision," he told reporters.

He said his decision to run for president was "a party decision, a decision of President Duterte".

The president and vice-president are elected separately in the Philippines and usually the country's top two elected officials come from different parties.

Mr Duterte, who cannot seek a second term under the Constitution, had earlier abandoned a bid to run for vice-president.

On Oct 2, he said he was retiring from politics because "the overwhelming sentiment of the Filipino people is that I am not qualified, and it would be a violation of the Constitution".

"I now say to my countrymen, I will abide by your will, and today I announce my retirement," he said.

Saturday's developments suggest that Mr Go and Mr Duterte may now go head-to-head with an opposing ticket made up of Ms Duterte-Carpio and former senator Ferdinand Marcos.

Mr Marcos' own political party has announced that it is "adopting" Ms Duterte-Carpio as its candidate for vice-president.

Lakas, Mrs Arroyo's party, is, in turn, expected to endorse Mr Marcos as its candidate for president.

"The party is in the process of formalising the adoption of a standard bearer whom Sara will be running with as president," said Lakas chairman Ramon Revilla on Saturday.

Responding to the latest turn of events, labour leader Leody de Guzman, who is running for president, said they were "nothing but a telenovela" being cooked up by the Dutertes.

Boxing sensation Manny Pacquiao, a senator who is likewise running for president, said he welcomed Ms Duterte-Carpio's decision to throw her hat into the ring.

But he said the way she entered the race was disingenuous.

"I would like to remind voters to think clearly because it seems like they're toying with us. They will promise anything just to get elected. But have they ever delivered on any of their promises?" said Mr Pacquiao.

Senate president Tito Sotto, the top pick for vice-president in opinion polls who now faces the prospect of running against both Mr Duterte and Ms Duterte-Carpio, said "it doesn't matter to us who else is running".

"We are focused on our government, our programme and platform for good governance," he said.

Ms Duterte-Carpio has for months denied that she had any interest in succeeding her father as president and her political future seemed destined to end in Davao city, with her serving three more years as mayor.

She registered to run for re-election as Davao mayor last month, insisting that the last thing she wanted was to be in the middle of a long, gruelling national campaign.

But, on Tuesday (Nov 9), she suddenly announced that she was withdrawing her candidacy for mayor without saying what she intended to do after that.

Then, on Thursday, she joined Mrs Arroyo's party.

Throughout this week, rumours were rife that Mr Duterte's camp was pressuring Mr Marcos to step down and run instead for vice-president under Ms Duterte-Carpio because his chances were weakened by a disqualification case filed against him.

Lawyers from an opposing political coalition have asked the poll commission to cancel Mr Marcos' certificate of candidacy on account of a previous conviction for tax evasion.

Elections will take place in the Philippines in May next year for a myriad of positions from president, vice-president, governors, mayors and local officials. The window for changing candidates expires on Nov 15.