Right-wing candidate, 41, has pledged to roll back parts of the landmark 2016 peace accord with the FARC group.

Conservative Ivan Duque has won Colombia’s presidential election, putting the landmark 2016 peace deal with the FARC at risk.

Duque secured 54 percent on Sunday, more than 12 points ahead of his leftist rival, Gustavo Petro.

He is first to be elected since outgoing President Juan Manuel Santos signed the peace accord with the Revolutionary Armed Forces of Colombia (FARC), formally ending more than 50 years of conflict.

“This is the opportunity that we have been waiting for – to turn the page on the politics of polarisation, insults and venom,” Duque told jubilant supporters Sunday night, joined by his young family.

In the capital, Bogota, enthusiastic Duque supporters honked car horns even before final results were announced.

“I’m euphoric because Duque won,” said Julio Palacios, who works in real estate in Duquista.

“I’m happy because of his economic policy, he is going to incentivise business and generate more employment,” he told Al Jazeera.

Those who supported Petro, however, fear Duque’s win will mean “more of the same”.

“I am not surprised, but I am disappointed,” Linda Lopez, a university student, said.

“It worries me that Duque could go back on the peace process,” she told Al Jazeera. “The next four years will be difficult.”

In May’s first round, Duque came first with nearly 40 percent of the vote, while Petro received 25 percent.

Fragile peace deal

The second round of voting was seen by some as a referendum on the controversial peace deal, which brought an end to 52 years of conflict that left at least 220,000 people dead and more than seven million displaced.

Most of the more than 7,000 rebels who have surrendered their weapons have started new lives as farmers, community leaders and journalists.

Duque is supported by former-president, Alvaro Uribe, one of the peace accord’s fiercest critics for its perceived soft judicial treatment of “FARC terrorists”. Duque says his party “does not want to tear the agreement to shreds” but rather “make it clear that a Colombia at peace is a Colombia where peace meets justice”.

The current agreement allows most rebels to avoid jail, a sore point for many.

“I am in agreement with peace, but not with the peace accord,” Palacios said. “It has to be revised. The FARC have to pay for the crimes they committed in some way.

Crticis, however, are unsure what Duque’s win will mean for the accord and the peace process itself.

“I’m upset for the victims of the conflict,” Isabel Montenegro, who works in social communications, told Al Jazeera.

“The future is uncertain for the victims if the FARC return to war because the peace process fails, we will go back to the past,” she added.

FARC, which disarmed and transformed into a political party after the peace deal but did not contest the election, immediately called on Duque to show “good sense” in dealing with the agreement.

“What the country demands is an integral peace, which will lead us to the hoped-for reconciliation,” the FARC said in a statement after Duque’s presidential win.

The former rebels also called for an early meeting with the president-elect.

In a concession speech that at times sounded celebratory, Petro challenged Duque to break with his hardline allies and Uribe, in particular. He also promised to mobilise his considerable following into a combative opposition that will fight for social reforms and defend the peace accord.

“Those eight million Colombians are not going to let Colombia return to war,” Petro said to a thunderous applause from supporters chanting “Resistance!”

Challenges ahead

Duque will face significant challenges when he takes office in August. The economy remains weak; drug trafficking gangs have moved into areas once controlled by the FARC and more than half a million Venezuelans have crossed into Colombia, looking for food and work.

A one-term senator, Duque worked at the Inter-American Development Bank in Washington until 2014, when Uribe asked him to return to Colombia and take a seat in Congress. Duque’s running mate, Marta Lucia Ramirez, will be Colombia’s first female vice president.

Duque has also promised to bolster the $324bn economy, keep investors happy by cutting business taxes, support the oil and coal sectors – top exports – and help manufacturing.

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For his part, Petro – a former Bogota mayor – pledged to take on political elites, redistribute land to the poor and gradually eliminate the need for oil and coal in

Duque’s victory means he will be Colombia’s youngest president since 1872. His swearing-in ceremony will take place in August.

With additional reporting by Luke Taylor in Bogota.