BOGOTA, Colombia -- Former Finance Minister Oscar Ivan Zuluaga finished first in the opening round of Colombia's presidential election Sunday, delivering a blow to President Juan Manuel Santos' re-election bid but failing to win enough votes to avoid a runoff ballot with the incumbent.
With nearly all polling stations counted, Zuluaga had 29 percent of the votes, compared to 25.5 percent for Santos. Conservative Party candidate Marta Lucia Ramierz was in third of the five-candidate field with less than 16 percent.
Zuluaga needed 50 percent plus 1 vote to win outright, and now will face Santos in a June 15 second-round election.
Relentless mudslinging in the campaign's final stretch and the arrest of a campaign adviser on charges of spying appeared not to have eroded support for Zuluaga, who emerged as Santos' toughest challenger thanks to the backing of his one-time boss and mentor, the still-popular former President Alvaro Uribe.
The runoff is likely to prolong a bitter showdown centered on the future of peace talks with the Revolutionary Armed Forces of Colombia, or FARC, and the conservative Uribe's polarizing legacy for improving security through a no-holds-barred military offensive.
As Uribe's defense minister and now president, Santos is credited with handing the rebels some of their biggest defeats, but he made a peace negotiations initiated 18 months ago with the FARC the centerpiece of his campaign.
Concerns that rebel leaders, on the ropes after a decadelong U.S.-backed offensive, will not be punished for any crimes have been fueling mistrust of the negotiations. Although Zuluaga said he also favors a negotiated settlement, he has said that if elected he would give FARC negotiators in Cuba a week to demonstrate their commitment to peace by declaring a permanent cease-fire.
Zuluaga also has threatened a tougher stance on Venezuela, saying in a debate this past week that he would not remain "silently complicit" as Venezuelan President Nicolas Maduro jails opponents and stamps out anti-government protests. Santos has been careful not to provoke the socialist Maduro, calculating that extensive commercial ties with Venezuela and relations with other leftist governments in South America could suffer.
But those policy differences were largely swamped in the past two weeks by a string of bitter attacks and startling revelations.
It began with media reports that Santos' campaign manager, J.J. Rendon, received $12 million from the nation's biggest drug traffickers to help negotiate their surrender. Rendon quickly resigned after acknowledging he interceded in the case, though he denied taking any money.
Meanwhile, Zuluaga's campaign came under fire after the arrest of a computer expert who worked for him on allegations he had hacked into the emails of the president and FARC negotiators.
Zuluaga denounced the arrest as a desperate ploy to derail his campaign. But the emergence of a clandestinely shot video where the candidate listened as the alleged hacker outlined his strategy to undermine the peace talks cast doubt on his claim that he had no knowledge of the consultant's alleged activities.
The tensions came to a head in a feisty exchange at a televised debate where Santos accused his rival of being Uribe's "puppet" and Zuluaga fired back: "You must show me respect."
None of the other candidates were able to capitalize on the last-minute feuding. It apparently did disgust many voters, however. Only 40 percent of the 33 million eligible voters bothered to cast ballots, producing Colombia's lowest turnout in four decades.
Regardless of who eventually wins the presidency, the polarizing rancor unleashed by the race won't be easy to mend.
"The entire political class comes out looking bad," said Ivan Garzon, a political scientist at the University of the Savannah in Bogota.