It was the outcome millions of Colombians had hoped to avoid: A bitter run-off between two presidential candidates whose polarising viewpoints once again leave the nation divided.
Conservative former president Alvaro Uribe, who opposed the FARC peace deal, exerts a powerful influence on voters in Colombia, but the left was still able to achieve a record score in Sunday's first round of the presidential election, in which turnout was sharply higher than usual.
Here are five factors that could influence the June 17 runoff between Uribe-backed conservative Ivan Duque and leftist Gustavo Petro. The winner succeeds Juan Manuel Santos, a Nobel Peace Prize laureate who leaves office in August.
1. The power of Uribe
Duque garnered 39.14 percent of the vote on Sunday, making him the top vote-getter but still short of an outright win.
His success is based in part on the popularity of his mentor, the former president and now senator Alvaro Uribe.
The vote "again shows the importance of Uribismo," said analyst Andres Macias of the Externado University.
It was the third time that Uribe, who waged an all-out war against the FARC as president from 2002 to 2010, has found himself at the center of a presidential race.
In 2010, Uribe backed Santos, his former defense minister, to succeed him as president. After Santos won the presidency, the two men had a bitter falling out and in 2014 Uribe threw his support to Oscar Ivan Zuluaga, who lost to Santos in a runoff.
Now, Uribe is championing Duque's presidential bid, and appears on the brink of reclaiming power through his new protege.
2. Alliances will be crucial
Alliances will play a key role in the second round.
Duque ran with conservative former minister Marta Lucia Ramirez as his vice presidential candidate, with the support of evangelical Christians as well as the far-right.
On Sunday night, he appeared to extend a hand to the former center-right vice president German Vargas Lleras, who came fourth with just 7.2 percent of the vote, and whose party is the third largest in Congress.
Petro, who came in second with 25.08 percent of the vote, hopes he can draw on support from divided centrists when he faces off against Duque.
But neither the ex-mayor of Medellin, Sergio Fajardo (third with 23.7 percent), nor former peace negotiator Humberto de la Calle (2.06 percent) have come out to support him.
Petro may also be able to lure votes from the 47 percent of the electorate that did not turn out in the first round. Typically, participation increases in the second round. The turnout in the first round was an already high 53 percent.
"The alliance that Duque will very soon be seeking will be with Vargas Lleras, while Fajardo and De la Calle will be difficult to convince," said political analyst Sebastian Bitar of Andes University.
3. The peace factor
The future of the historic peace accord with the Revolutionary Armed Forces of Colombia (FARC), a guerrilla group turned political party, has emerged as a key and divisive issue in the elections.
Duque has vowed to rewrite the accord if elected, arguing that rebel leaders got off too lightly and calling for a "Colombia where peace coincides with justice."
For that, he would be able to count on the support of Uribe's Democratic Center party, which swept legislative elections in March and now enjoys a near majority in the Congress.
Key aspects of the peace accord, including a system to judge ex-guerrillas and military officers responsible for crimes during the conflict and agrarian reform, have yet to be implemented by the Congress.
Duque also wants to review the dialogue launched with the smaller National Liberation Army (ELN) guerrillas.
Petro has said he would honor the FARC accord and supports talks with the ELN but he lacks a base of support in Congress.
4. The success of the left
The left on Sunday scored its best ever performance in a Colombian presidential election, a significant achievement in a country traditionally governed by the right.
Petro, an ex-mayor of Bogota and a former member of the M-19 guerrilla group, picked up 4.8 million votes, enough to send him into the runoff with Duque.
That beat the previous best by a leftist presidential candidate, in 2006, when Carlos Gaviria received 2.6 million votes but was defeated in the first round by Uribe.
But Petro's sympathies for the leftist policies espoused by Hugo Chavez, the late Venezuelan leader, has hurt him with Colombian voters at a time when Venezuela is in deep turmoil.
5. Turnout at over 50 percent
Turnout rarely surpasses 50 percent in the country of 49 million people.
But on Sunday, 53.29 percent of eligible voters, or 19.6 million people, cast ballots.
In the first round in 2014, that figure was 13.2 million, then 15.7 million in the second.
"There was an increase in turnout, but the abstention rate was still high. It remains to be seen if that can work in Petro's favor," said Medofilo Medina of National University.