MANILA – Voters dealt President Ferdinand Marcos Jr a stinging protest vote in the Philippines’ midterm elections that weakened his grip on the Senate, while boosting Vice-President Sara Duterte’s allies just weeks before an impeachment trial against his deputy.

Early results also showed independent opposition candidates performing stronger than expected at the May 12 polls.

Some 68.43 million voters went to the polls to elect more than 18,000 officials nationwide to fill half of the 24-seat Senate, all 316 seats in the House of Representatives, and thousands of local posts – from mayors to governors and their deputies in every province, city and town.

Partial, unofficial results by 11.11pm, with 75.45 per cent of results transmitted, showed Mr Marcos’ Alyansa Para sa Bagong Pilipinas (Alliance for a New Philippines) slate winning only six of the 12 contested Senate seats – well below the nine predicted by pre-election surveys.

Ms Duterte’s slate picked up five seats. Mr Bong Go, a longtime aide to her father, former president Rodrigo Duterte, has clinched 25.6 million so far – the most number of votes among the candidates vying for one of 12 contested Senate seats.

One Senate seat was claimed by a candidate endorsed by both factions: Ms Camille Villar, daughter of Filipino billionaire Manny Villar, who remained on Mr Marcos’ slate but aired campaign ads with Ms Duterte in the final stretch of the campaign. As the votes were tallied, Ms Villar was counted under both Mr Marcos’ and Ms Duterte’s victories.

But the strongest rebuke to the political status quo came from outside the Marcos-Duterte camps.

Opposition candidates critical of both factions made an unexpected breakthrough. Former senator Bam Aquino is placing second with 20 million votes in the Senate race, while former vice-presidential contender and senator Kiko Pangilinan is fifth with 14.7 million – both outperforming their pre-election survey rankings.

“This is a protest vote against the Marcos administration. It’s very apocalyptic for Alyansa,” Dr Aries Arugay, visiting senior fellow at the ISEAS-Yusof Ishak Institute in Singapore, told The Straits Times.

He said that the results exposed the limits of Mr Marcos’ political capital.

“His endorsement i...