BOGOTA, Colombia (AP) — The party of Colombian President Gustavo Petro secured a victory in congressional elections, but will have to build coalitions with other parties to carry out announced reforms, including a controversial push to rewrite the nation’s constitution.

Petro's Historical Pact party won almost a quarter of all seats in the Senate on Sunday and about 15% of seats in the House of Representatives, more than any other party.

But its staunchest opponents also made gains, with the Democratic Center — the conservative party led by former President lvaro Uribe — securing 17 seats in the 103-member Senate.

Traditional parties including the Liberals and Conservatives lost ground in the Senate, while the Green Party also saw a smaller showing.

“The country seems to be turning away from voices in the center, and it's becoming more polarized,” said Carlos Arias, a political consultant based in Bogota.

Jorge Restrepo, an economist at Bogota’s Javeriana University, said the election results showed that Colombia, a nation governed for decades by technocratic administrations on the center and the right, is no longer “immune to populism.”

“The Petro administration has taken a series of measures that are popular in the short term” but not sustainable in the long term, Restrepo said.

He pointed to a massive increase in the nation’s minimum wage, decreasing gasoline prices and reforms to the nation’s labor laws that have increased overtime payments.

“These decisions have helped to increase the popularity of the Historical Pact,” Restrepo said. “And make its critics more unpopular.”

The congressional election came just two months before Colombia holds a presidential election that will be crucial for the nation’s security policies and for the continuation of economic reforms led by the current government.

During its four years in power the Petro administration has pushed for negotiations with the nation’s remaining rebel groups while overhauling labor laws that recently included a 23% increase to the nation’s minimum wage — despite a 5% inflation rate last year.

Petro has said he would like to nationalize Colombia’s health care system, so that private insurance companies no longer handle social security payments. He has also pushed for changes to the pension system that would enable the government to administer a greater portion of pension payments.

Petro opponents have threatened to roll back some of these reforms, which they argue lead to wasteful government spending.

They have also signaled a more confrontational approach toward rebel groups that have increasingly threatened civilians with extortions, kidnappings and death threats, as they fight over territory and finance themselves with cocaine exports.

On Sunday, a coalition of parties on the center and the right held a presidential primary in which they elected Paloma Valencia, a senator for the Democratic Center, as their presidential candidate.

The coalition picked up 5.7 million votes, which turned Valencia into a serious contender in the upcoming elections, said Sergio Guzm n, a political risk analyst in Bogota.

Petro is barred from running in the election by Colombia’s constitution. But his party’s candidate, Sen. Iv n Cepeda is ahead in polls, followed by Abelardo de la Espriella, an ultra conservative lawyer who has described himself as an admirer of Salvadoran president Nayib Bukele.

Sunday’s showing by Valencia suggests that she could now compete with De la Espriella for Colombia’s conservative vote.

“Abelardo’s candidacy seems shaky now,” Guzm n said, adding that the lawyer’s congressional list gained around 600,000 votes on Sunday, just a tenth of the votes cast for the primary won by Valencia.

There will be at least half a dozen candidates competing in May’s presidential election, including two members of smaller left-wing parties.

If none of the candidates gets 50% of the votes a run off will take place in June between the top two contenders.

Yan Basset, a political science professor at Bogota’s Rosario University, said that a victory by a conservative candidate would kill existing efforts by the Petro administration to rewrite Colombia’s constitution.

Petro has argued that a constitutional reset is required to empower voters and advance economic reforms previously blocked by the nation's judges. But critics describe the effort as a power grab intended to diminish judicial oversight over the nation's executive branch.

Basset said that if Cepeda, the Historical Pact candidate, wins the election, his government would struggle to change the constitution, due to the new makeup of Colombia’s Congress.

“The left won, but they only had a quarter of the seats,” Basset said. “I don’t think that there is the appetite among their potential coalition partners” to change the constitution.

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