BOGOTA, Colombia (AP) — Conservative political outsider Abelardo de la Espriella held a razor-thin lead Monday after Colombia's deeply polarized presidential runoff, which is being challenged by the ruling party's progressive candidate.

De la Espriella, a business owner and lawyer who earned U.S. President Donald Trump's endorsement despite never having run for office, led progressive lawmaker Iván Cepeda, taking 49.7% of the votes, with 99.9% of results released by electoral authorities. Cepeda, Petro's ally, earned 48.7% support. Election officials have not formally announced a winner.

A victory by de la Espriella is expected to usher in policies that will reverse the agenda of outgoing President Gustavo Petro, including a controversial plan to hold parallel peace negotiations with illegal armed groups. Cepeda, Petro's protégé, had pledged to push forward that strategy and other social reforms if he won Sunday's vote.

The election was colored by people's fears of a renewed internal conflict.

"I will govern for all Colombians," de la Espriella, nicknamed "The Tiger," told thousands of supporters as he stood behind bulletproof glass in the northern city of Barranquilla on Sunday night. But his conciliatory tone changed as he spoke.

"Pack your bags and prepare to exercise the opposition," he added. "Make no mistake, Mr. Cepeda. You already know how fiercely the tiger roars."

Progressive candidate calls count 'unofficial and nonbinding'

Meanwhile, Cepeda told supporters in the capital, Bogota, that his campaign considered the count "unofficial and non-binding" and that his team will challenge results from more than 30,000 voting stations. No recount has flipped the results of a presidential election in Colombian history.

"We will not allow democracy to be violated," Cepeda said.

Petro also vowed to challenge the outcome. Sunday's winner will begin a four-year term Aug. 7.

People in the western city of Cali protested hours after results became public. The vote count showed that the municipality that includes the city favored Cepeda with 59.64%.

Authorities there said demonstrators damaged a public transportation bus, several surveillance cameras and an ATM. They said four police officers were also injured and two demonstrators were arrested.

The two candidates pitched voters widely different strategies to prevent the South American country from experiencing the nonstop violence, such as car bombs, kidnappings, disappearances and forced displacements, that Colombians lived with in previous decades.

De la Espriella, 47, promised a heavy-handed approach to crime-fighting, including drug trafficking. He also said he plans to end Petro's attempts to establish dialogues with multiple armed groups — an effort that has largely failed — and build mega-prisons, emulating Salvadoran President Nayib Bukele's aggressive policies. Those tactics have lowered homicide rates in the Central American country but have fueled accusations of human rights abuses.

De la Espriella holds dual Colombian and U.S. citizenship. He's a Trump supporter and a member of the Republican Party.

"He Won, BIG!" Trump said on his social media platform.

'It's always the same violence'

Yolanda Hernández, who recycles trash for a living, voted for Petro in 2022, but cast her ballot for de la Espriella this time. While she acknowledged that Petro was unable to deliver on promises meant to help the poor because of congressional gridlock, she said Colombia cannot afford another four years under his vision for the country.

"We want change in Colombia because it's always the same violence, always the same thing," Hernández, 49, said. "(Petro) said he was going to lower the cost of services, that he was going to lower the price of food, and everything is more expensive."

Will Freeman, a fellow for Latin American Studies at the Council on Foreign Relations, said Sunday's result shows the country "has not shifted overwhelmingly or decisively" against Petro's project or for de la Espriella's outsider "iron fist showmanship." Freeman added that the result also underscored Colombia's regional divisions.

"It's regional not just ideological polarization; or rather, the two overlapping," he said. "Ironically, de la Espriella's iron-fist message performed best in the core of the country, not the periphery, which bears the brunt of Colombia's violence."

Colombia's illegal groups have more than 27,000 members.

Last year, authorities recorded 14,780 homicides, the most since at least 2015, driven by clashes among illegal armed groups. Among those killed was conservative presidential hopeful Miguel Uribe.