Marcos-Duterte battle in focus ahead of Philippines midterm election 

Registration gets underway in the Philippines on Tuesday for one of the world's biggest midterm elections, headlined by what could be a bitter proxy battle between President Ferdinand Marcos Jr and fiery predecessor Rodrigo Duterte.

The May 2025 election will be a litmus test of Marcos' popularity and a chance to consolidate power and groom a successor, which the influential Duterte family has signalled it is determined to stop after an acrimonious falling out.

Philippine presidents are limited to a single, six-year term.

Though 317 seats in Congress and thousands of regional and city posts are up for grabs among 18,000 positions, the attention is on 12 spots in the 24-seat Senate, a high-profile chamber with outsized influence and typically stacked with political heavyweights.

Speculation has swirled that the mercurial Duterte, 79, and two of his sons will contest the senatorial race to try to weaken Marcos. Duterte's office and that of his daughter, Vice President Sara Duterte, did not immediately respond to requests for comment.

The midterms come after the collapse of what was an unstoppable alliance between the two families that delivered a landslide election win for Marcos in 2022. Sara Duterte had been frontrunner for president in surveys but opted instead to become Marcos' running mate.

But their relationship has since turned hostile, owing to policy differences, the unravelling of Rodrigo Duterte's pro-China foreign policy and investigations into his bloody war on drugs, plus other scandals implicating his associates.

Sara Duterte resigned from cabinet and last week suffered a humiliating two-thirds slashing of her office's budget by a Congress led by the president's cousin, after she refused to attend hearings and objected to scrutiny of her spending.

POWERFUL PLATFORM

Senate seats could give the Dutertes a powerful platform in the Philippines' personality-driven politics to shore-up support, challenge Marcos legislation and initiate investigations into his government.

"All eyes will be indeed on who among them would run ... or all of them," said Ederson Tapia, professor of public administration at the University of Makati.

"The Dutertes, notwithstanding the controversies hounding VP Sara, remain a formidable force."

Marcos is bolstering his base by endorsing big local names for the Senate, including three former movie actors, the daughter of the country's richest man, plus two of his presidential election rivals, among them global boxing icon Manny Pacquiao.

A notable absence from his Senate slate will be sister Imee Marcos, however, who is seeking re-election but declined her brother's endorsement, which she said was to avoid putting him in a difficult position.

Political science professor Jean Encinas-Franco of the University of the Philippines said success for President Marcos in the midterms could be vital to his legacy.

"If the majority of those he endorsed win in the Senate and the House, it ensures that his legislative agenda will push through," she said.

"It ensures that he will have enough clout to anoint someone who he is going to support in the 2028 (presidential) elections."