A slate of candidates opposed to President Rodrigo Duterte of the Philippines is waging an uphill battle in elections set for Monday for the Senate, one of the last bulwarks against his strongman rule.
The police have killed nearly 5,300 people suspected of selling or using drugs since Mr. Duterte began a violent antidrug campaign, official statistics say. Rights groups estimate that the toll is much higher — more than 20,000 dead, many at the hands of pro-government vigilantes. The authorities say the killings were justified.
The election is a “historic fight against the resurgence of tyranny,” said an incumbent senator, Leila de Lima, who is in jail on drug-trafficking charges that she and rights groups say are trumped up.
Half of the Senate’s 24 seats are up for election in Monday’s vote, which is taking place at the midpoint of Mr. Duterte’s six-year term. The vote could weaken the upper chamber’s independence for years to come.
Unlike the House of Representatives, which has gone along with Mr. Duterte’s war on drugs, his declaration of martial law in the south and other measures, the 24-seat Senate has been seen as more independent. Six members of the opposition are in the minority bloc, while the rest are allied with the president.
But public opinion polls suggest that a further shift toward Mr. Duterte and his allies could happen in Monday’s vote. In a survey conducted in late March by Social Weather Stations, an independent polling company, 81 percent of respondents said they were satisfied with Mr. Duterte’s administration.
“Many Filipinos continue to believe in his promises of change, including the relentless campaign against criminality, corruption and illegal drugs,” said Bong Go, a onetime personal aide to Mr. Duterte who is among the presidential allies running in Monday’s election.
Mr. Duterte’s trusted national police chief, Ronald dela Rosa, who carried out the first phase of his drug war, is also among those candidates.
Opposition to Mr. Duterte in the Senate had been already weakened by the 2017 jailing of Senator de Lima, one of his most vociferous critics. Another prominent anti-Duterte senator, Antonio Trillanes, is not seeking re-election.
Most of the anti-Duterte candidates in Monday’s election carry long odds, according to the polls.
One of them, Chel Diokno, a human rights lawyer, has taken on Mr. Duterte’s antidrug war in the courts, helping relatives of some of the thousands of Filipinos who have been gunned down by police officers or vigilantes.
Mr. Diokno, who teaches at De La Salle University College of Law, said that despite the odds, he was inspired by what he said was growing support. The president has verbally attacked him, which he said had helped to raise awareness of his candidacy.
“I realized that silence is no longer an option when people started being killed every day and our democratic institutions are being attacked,” Mr. Diokno said after a campaign rally in Manila on Wednesday, where he spoke to an enthusiastic crowd and was endorsed by prominent former judges and prosecutors.
If elected, Mr. Diokno said, he will try to address the low conviction rates in the Philippine courts, which many see as a reason Filipinos have welcomed Mr. Duterte’s bloody antidrug campaign.
Still, only two of the eight anti-Duterte candidates running on Monday are seen as having a good chance of winning: Mar Roxas, an ally of former President Benigno S. Aquino III who lost the 2016 presidential election to Mr. Duterte; and Bam Aquino, the former president’s cousin who is seeking re-election.
Jose Antonio Custodio, a historian and political analyst at the Institute of Policy, Strategy and Development Studies, said that Mr. Duterte’s popularity among poor Filipinos was likely to benefit his allied Senate candidates.
Noting that many of the president’s Senate supporters had been implicated in corruption scandals, he said a pro-Duterte majority in the chamber would be “open to the highest bidder, with an opposition that would be effectively smothered.”
Senator de Lima, who is being detained at Philippine National Police Headquarters in Manila, went further, saying in an interview that the Philippines risked “another long period of strongman rule” should Mr. Duterte’s allies gain greater control.
“This will bring the Philippines back to square one in its democratization and political modernization project,” Senator de Lima said.