President Juan Manuel Santos, right, who is seeking a second four-year term as candidate for the Social Party of National Unity in the upcoming June 15 presidential election runoff, shakes hands with Oscar Ivan Zuluaga, candidate for the Democratic Center, prior to a televised presidential debate in Bogota, Colombia, on May 22. (Fernando Vergara/AP)

The two sides meet in a drab Havana conference room, lifelong adversaries who are responsible — directly or indirectly — for the deaths of each other’s comrades, friends, even family members.

There is no idle chitchat at coffee breaks. After long sessions of incremental dealmaking and minutiae, the Colombian government negotiators and FARC guerrilla leaders do not retire to a veranda for rum and cigars.

“Relations are cordial and respectful, but austere,” said Gen. Óscar Naranjo, when asked what it was like sitting down day after day with mortal enemies. “If we’re going to end this conflict, you have to put aside personal feelings.”

The former commander of Colombia’s National Police, famous for helping bring down drug lord Pablo Escobar, Naranjo has been at war with FARC commanders much of his life. Back in Colombia, they would probably kill him if they could.

But Naranjo and the other high-level negotiators are in Cuba to make peace, with the backing of Colombia’s key counterinsurgency ally, the United States. This is the government’s fourth attempt to hash out a truce with the Revolutionary Armed Forces of Colombia, a group that has been at war with the state since 1964, yet no previous effort has come so far.

After 18 months of formal talks, the accords are more than halfway complete, and now face their biggest and perhaps toughest test: the June 15 presidential runoff between incumbent Juan Manuel Santos and challenger Óscar Iván Zuluaga.

Santos has framed the race as a choice between war and peace, telling voters that “there’s no going backward” and that a win by his opponent would mean “war without end.”

But having FARC guerrillas as his de facto running mates has been costly for Santos. He fared poorly in the first round of Colombia’s presidential election on Sunday, winning just 26 percent of the vote, while Zuluaga finished first among five candidates with 29 percent.

‘Peace without impunity’

Many Colombians are deeply wary of the peace talks. They see FARC commanders smiling for television cameras and issuing grand indictments of the government from the comforts of Havana, while not appearing especially repentant.

Zuluaga, a former finance minister, has tapped into fears that the negotiations will allow FARC leaders to wiggle off the hook with a wrist-slap, despite multiple convictions for murder, drug trafficking, kidnapping and terrorism-related crimes.

“Peace without impunity” has been Zuluaga’s campaign slogan, while he blasts Santos as a pushover who is “allowing the FARC to run Colombia from Havana.”

Zuluaga’s demand that the FARC agree to a unilateral cease-fire is viewed as a deal-breaker, not least by the jungle commanders who continue battling government troops as the talks unfold. They say they’ll never accept a “humiliating surrender.”

Zuluaga is the political scion of powerful former president Álvaro Uribe, who dealt heavy losses to the FARC between 2002 and 2010, killing many of its top leaders and cutting its ranks from an estimated 20,000 fighters to fewer than half that.

But the FARC has started to bounce back, skimming profits from Colombia’s mining and oil drilling boom, and the government acknowledges that the insurgents retain the ability to fight for years more.

“Uribe convinced Colombians that the FARC was a washed-up group of terrorists and drug traffickers on the verge of defeat, with no social support,” said security analyst León Valencia, himself once a guerrilla commander with the smaller ELN group. “But if they’re in such bad shape, why are we negotiating with them?”

Santos has been hurt by the perception that the talks are taking too long or amounting to little, but government negotiators point to successful cease-fire treaties in Northern Ireland, Guatemala and elsewhere that took years to hammer out.

The negotiators have also extracted significant concessions from the FARC, which seems to have essentially abandoned the revolutionary Marxist agenda it has espoused for decades.

More-modest goals make up the peace plan’s five-point agenda. Three points have been agreed upon so far, but none takes effect until all five points are settled and Colombian voters approve the entire package in a referendum.

Until then, the specific details of each point of agreement are to remain secret, so only the broad outlines are known.

The agreement so far

The first, rural reform, would mostly lay the groundwork for more-robust development and better services in the poor rural areas that are FARC bastions.

The second point paves the way for demobilized FARC members to eventually participate in electoral politics, if cleared of criminal charges.

The third agenda item, announced May 16, is considered the most significant to date, as it compelled the FARC to acknowledge its role in drug trafficking. The group agreed to sever all ties with the narcotics trade and help implement crop substitution programs in areas where coca and opium poppies are a mainstay.

In exchange, the government pledged to abandon its deeply resented, U.S.-backed aerial spraying campaign, while still reserving the right to use herbicides when manual eradication is not possible.

Two sticky points remain on the table: one related to the nuts-and-bolts of the demobilization process and surrender of FARC weapons, and another to determine potential criminal penalties for FARC leaders and reparations to victims.

“Victims have to be at the center of this process,” said Sergio Jaramillo, the government's high commissioner for peace, and the man considered the architect of the accords. “The question must be: How are we going to end this conflict together, and deliver the best sense of satisfaction for the victims?”