The bill also granted the runner-up candidate in a presidential election a seat in the senate, whilst their running mate would become a member of the chamber of representatives.

Duque, who was mostly unknown to the public before the election,[3] had a platform encompassing support for innovation, economic recovery and staunch opposition to the peace agreement.

[5] Petro, a former AD/M-19 member and nominee for the Humane Colombia party, ran a progressive populist campaign that focused on reducing inequality and implementing universal healthcare and environmental protection.

The bill faced criticism from supporters and members of the Democratic Center party led by former president and rival of Santos, Álvaro Uribe.

[16] Legislative act # 2 of 2015 established that the runner-up in the presidential elections is given a seat in the Senate and their Vice President candidate will become a member of the House of Representatives.

[30] Viviane Morales and her vice presidential candidate Jorge Leyva Durán, of the Somos Región Colombia party, retired their candidacy on 2 May 2018.

[2] Iván Duque, a lawyer, senator, protege of Uribe, and the nominee for the Democratic Center party, campaigned on promoting innovation, job creation, economic recovery, environmental preservation and opposing the FARC peace agreement.

Due to Duque's youth and light experience, opponents and critics painted him as unprepared to head the executive branch, leading some to claim further that the senator was a puppet of Uribe.

[41][42] Economist Gustavo Petro of Humane Colombia, a former mayor of Bogotá and former M-19 guerilla who was previously a candidate in the 2010 presidential election, ran a populist campaign focusing on decreasing inequality and tackling climate change.

Supported by a coalition of left and centre-left parties, Petro also emphasised workers' rights and campaigned to improve labour conditions in both urban and rural areas.

Critics said his policy proposals would not attract foreign investment and that his plans to abandon non-renewable energy, which accounted for 2-4% of Colombia's GDP, were not feasible at the time.

[43][44] Veteran politician Humberto De la Calle, who served as vice president to Ernesto Samper,[45] was the nominee for the Colombian Liberal Party.

De la Calle played a crucial role in negotiating the peace deal with the FARC and campaigned on policies to assist the country post-conflict, including investments in job creation and regions that were heavily affected by the conflict.

De la Calle supported increasing environmental protection and stricter criteria for the issue of mining licenses, both as a means of promoting ecotourism.

Due to the high presence of labour inequality and gender-based violence, De la Calle announced his intention to establish a ministry of women to tackle these issues.

De la Calle's proposals included other policies with broad support amongst the youth, such as modifying the unpopular student loan program and abolishing compulsory military service.

His 30 years of political experience proved a double-edged sword; some voters saw this as a benefit, but others concluded that De la Calle was a part of the elite.

Whilst he campaigned on being the fiscally reliable candidate, he faced criticism from opponents who highlighted a dramatic debt increase that occurred during his tenure as governor of Antioquia.

Trujillo, the founder of the gospel church of Casa de Reino, gained widespread attention in 2014 when he claimed that the winter wave the country experienced was a punishment from God and blamed President Santos, claiming that the president had previously travelled to the Sierra Nevada de Santa Marta mountains where he made a "secret rite" and "handed over the country to the shamans and sorcerers."

On the economy, the former vice president supported lowering income taxes to attract more foreign investment and promote entrepreneurs, differing from the policy of the Santos administration.

Critics said his tax reform proposal would risk increasing inequality throughout Colombia and that the support from president Santos would prove to be a double-edged sword due to the outgoing administration's unpopularity.

[60] The Eje Cafetero debate was cancelled due to disturbances that prevented some candidates entering the Los Fundadores de Manizales theatre.

Afterwards Iván Duque, Humberto de La Calle, Gustavo Petro and Germán Vargas Lleras met at the city's auditorium and held a closed-door debate.

These candidates were; Iván Duque, Gustavo Petro, Sergio Fajardo, Germán Vargas Lleras, Humberto De la Calle and Jorge Antonio Trujillo.

[63] The Alternative Democratic Pole joined Gustavo Petro's campaign, but a minority sector led by Senator Jorge Robledo (MOIR) decided to vote blank too.

[65] Movimiento Mejor Vargas Lleras and the Radical Change party sent their former candidate's program to Iván Duque, to consider it for a future government, although there was not an official adhesion.

[66] The Partido de la U and the Social Party of National Unity encouraged their followers choose freely to vote for their preferred option.

Because he failed to attain the 50% required to win an outright victory, Duque, along with the second-place candidate Gustavo Petro who received 25.09%, competed in a second round.

Duque secured a majority of the vote in 23 departments and received a plurality in La Guajira, while his strongest showing was in Norte de Santander, where he earned 77%.