Portugal Colonial - Presidential candidates refuse to back rival Robredo in Philippine race

Voter surveys show Robredo is a distant second behind Marcos Jr, but a recent bump in the polls and huge crowds at her rallies have raised hopes among her fervent fans that the campaign is gaining traction.

There has been speculation that worse performing candidates were considering pulling out and endorsing Robredo -- the incumbent vice president and only woman in the race -- to ensure Marcos Jr was defeated in the May 9 elections.

The latest Pulse Asia Research survey showed Robredo on 24 percent with Marcos Jr on 56 percent.

But in a vitriolic press conference on Sunday, Francisco Domagoso, Panfilo Lacson and Norberto Gonzales -- who are on single digits or less -- accused Robredo of trying to get them to withdraw and strip them of support.

"Each of us will continue with our respective presidential campaigns," Domagoso, a celebrity mayor, told reporters at a luxury hotel in Manila.

"I'm calling for Leni to withdraw because whatever you're doing is not effective against Marcos."

Analysts said it was not clear how many votes Robredo would gain from their exit in the raucous democracy where voter decisions were driven by personality rather than ideology.

But their backing would have energised her campaign, said Cleve Arguelles, an assistant lecturer in political science at De La Salle University in Manila.

"It would send a really strong signal to the other campaign that she has gained a new momentum," he told AFP.

- 'Bluster and falsehood' -

There are no runoffs in Philippine presidential elections, with the victor only required to win more votes than everyone else.

Lacson accused Robredo of "lying", claiming she had previously told him that she would not run for president. He also alleged she had exaggerated the crowd size at a recent rally.

"You deceive once, you deceive twice, you will deceive all the time," he said.

Domagoso, the top second preference for president in the Pulse Asia survey, said the polls were "polluted" and questioned their accuracy.

The candidates said rival Manny Pacquiao, who was not at the gathering, was also on board with their decision.

A member of Pacquiao's team tweeted the boxing legend would "never" quit the presidential contest.

Robredo's spokesman Barry Gutierrez accused the three candidates of "theatrics" and asserting their positions through "bluster and falsehood".

He did not respond to AFP's question about whether Robredo's team had asked the candidates to pull out.

Political analyst Tony La Vina said their decision to stay the course could actually help Robredo.

"They take more votes away from Marcos than they do from Robredo," he told AFP.

More than 18,000 posts are up for grabs in the national elections, from president all the way down to town councillor.

Robredo, who narrowly defeated Marcos Jr in the 2016 vice-presidential race, reluctantly entered the contest following pressure from supporters and opposition groups.

Marcos Jr has been boosted by a formidable alliance with first daughter and vice-presidential candidate Sara Duterte and a massive misinformation effort on social media.

M.A.Vaz--PC