Colombians choose a new president Sunday in a landmark election, the first since a peace agreement with FARC rebels which conservative frontrunner Ivan Duque wants to overhaul.
Offering a starkly different choice to voters is Duque's opponent, leftist former mayor and ex-guerrilla Gustavo Petro, who supports the deal in what has come to resemble a referendum on the 2016 agreement.
"We have a country without FARC, which is building peace," President Juan Manuel Santos, who will step down in August, said ahead of the poll. His efforts to end the war with FARC brought him the Nobel Peace Prize, though he is leaving office with record unpopularity in a country of 49 million people.
The world's leading producer of cocaine, the Latin American country continues to battle armed groups vying for control of lucrative narco-trafficking routes in areas FARC once dominated.
Duque comfortably won the first round last month, having campaigned on a pledge to rewrite the agreement signed by Santos.
Vehemently opposed to the peace deal, 41-year-old Duque says he would revise it in order to sentence guerrilla leaders guilty of serious crimes to "proportional penalties."
The former economist and first-term senator says he wants to cut off their access to representation in Congress, enshrined in the agreement, under which FARC transformed itself into a political party.
Duque is buoyed by the backing of his popular mentor, former president and now senator Alvaro Uribe, whose two-term presidency from 2002-2010 was marked by all-out war on the FARC.
Petro, 58, is the first leftist to reach a presidential runoff in Colombia, and believes his presence shows the South American country has shed its suspicions of the left, tainted by 50 years of conflict.
A former member of the disbanded M-19 guerrilla group, he says he will implement the agreement with FARC, which has transformed itself into a political party amid a struggle to integrate its 7,000 ex-combatants into civilian life.
Highlighting Colombia's glaring inequalities during his campaign, Petro has said that if elected he will buy out land owned by the big agro-industrial companies and redistribute it to poor farmers.
The latest polls show Duque, a candidate for Uribe's Democratic Center party, would beat Petro by between six and 15 points on Sunday.
- Peace biggest challenge -
"Whoever becomes president, the biggest challenge will be to adopt a clear position on the peace agreement because, for the moment, we are in limbo," Fabian Acuna, professor of political science at Colombia's Javeriana University, told AFP.
In the campaign's home stretch, both candidates have concentrated on forming the alliances seen as critical to victory.
Supporters of centrist ex-Medellin mayor Sergio Fajardo, who narrowly missed out to Petro in the first round with nearly 24 percent of the vote, will weigh heavily on the outcome.
Analysts believe Fajardo's supporters are less likely to support Petro and his best bet may be to lure votes from the 47 percent of the electorate that did not turn out in the first round.
If elected, Duque will become Colombia's youngest president since 1872. According to Andres Ortega of National University, he will "arrive with a very strong coalition in Congress," where the right swept the polls in March legislative elections.
FARC withdrew from the presidential elections having suffered a drubbing in its first electoral contest as a political party in March, polling less than half a percent.
It still gets 10 seats in Congress as a result of the peace agreement, something Duque is intent on scrapping.