Colombia’s President Gustavo Petro won a congressional election head start for his agenda, but Sunday’s results left him without the congressional majority needed to push through announced changes, including a controversial plan to rewrite the constitution, according to the Associated Press reporting. The administration’s party, the Historical Pact, captured nearly a quarter of seats in the Senate, the chamber where bloc strength tends to determine whether legislation can clear the math.

In the Senate race, the Historical Pact finished with the most seats of any party, while the Democratic Center—led by former President Álvaro Uribe—secured 17 seats in the 103-member chamber. The outcome meant Petro’s supporters would likely have to negotiate with other parties to carry reforms into law, AP reported.

The House results also underscored the bargaining problem. The Democratic Center received the most overall votes in the lower chamber, while the Historical Pact placed in fifth place in vote totals. The Associated Press noted that House votes do not always map directly to seat counts because a formula assigns seats by region, which could yield a different picture of representation than the raw vote totals suggest.

Political analysts interviewed by AP framed the election as a shift in Colombia’s political landscape. Carlos Arias, a political consultant based in Bogota, said the country “seems to be turning away from voices in the center, and it’s becoming more polarized.” Jorge Restrepo, an economist at Bogota’s Javeriana University, said the results showed Colombia was no longer “immune to populism,” adding that the Petro administration’s policies were popular with supporters in the short term even as they were, in his view, not sustainable over the long term.

Restrepo pointed to measures he said boosted the Historical Pact’s standing, including a massive increase in the national minimum wage, decreasing gasoline prices, and labor-law reforms that raised overtime payments. Restrepo also said, “These decisions have helped to increase the popularity of the Historical Pact,” and “make its critics more unpopular,” according to AP.

The congressional vote landed just two months before Colombia holds its presidential election, a contest that AP said will be crucial for security policies and for the continuation of economic reforms pursued by Petro’s current government. During the four years in power, AP reported, the Petro administration pushed for negotiations with the country’s remaining rebel groups while changing labor laws that included a 23% increase to the minimum wage, even amid a 5% inflation rate last year, according to the AP account.

Petro has also proposed changes to social welfare systems, AP said, including nationalizing Colombia’s health care system so private insurers would no longer handle social security payments. He has additionally pushed changes to the pension system that would allow the government to administer a larger share of pension payments, while opposition figures have threatened to roll back reforms they argue would lead to wasteful government spending, AP reported.

On Sunday, a coalition of center and right parties held a presidential primary and chose Sen. Paloma Valencia, of the Democratic Center, as its candidate. The coalition picked up 5.7 million votes, which made Valencia “a serious contender” for the upcoming presidential election, said Sergio Guzmán, a political risk analyst in Bogota.

Valencia’s showing also highlighted an opening for conservative competition. AP reported that the Historical Pact’s political strength in Congress comes alongside a conservative bloc preparing for the presidential contest, where Petro is barred from running again by Colombia’s constitution. AP said that Historical Pact candidate Sen. Iván Cepeda was ahead in polls, followed by Abelardo de la Espriella, an ultra conservative lawyer who described himself as an admirer of Salvadoran President Nayib Bukele.

As AP reported, the analysts said the congressional makeup could influence whether the constitutional overhaul sought by Petro can advance. Yan Basset, a political science professor at Bogota’s Rosario University, said a conservative victory would end existing efforts to rewrite the constitution, and he argued that if Cepeda wins, the new congress would make it difficult for his government to change the constitution because of the composition of Colombia’s legislature. Basset said, “The left won, but they only had a quarter of the seats,” and added, “I don’t think that there is the appetite among their potential coalition partners” to change the constitution, AP reported.