BOGOTA (Reuters) - Left-wing presidential candidate Gustavo Petro had a simple but radical proposal for his audience in the small industrial town of Yumbo in western Colombia.

Colombian presidential candidate Gustavo Petro speaks to supporters from the Liberal Party during a meeting at a hotel in Bogota, Colombia May 22, 2018. REUTERS/Henry Romero

What if his government bought a huge stretch of land owned by billionaire sugar baron Carlos Ardila Lulle close to the nearby city of Cali?

“It would be nice if he decided, once we are in power, to sell his Incauca farm to the government so we can give it to peasant farmers,” said Petro, a former rebel with the M19 urban guerrilla group, speaking during a rally on April 26.

The crowd roared approval for an idea that would not have sounded out of place in the platform of several leftist Latin American leaders in recent years but that seemed shocking from a mainstream candidate in Colombia.

For decades, the fractured left has failed to come close to winning Colombia’s presidency or exercising control in Congress, overshadowed by right-wing contenders who have promised strong security policies.

Yet a 2016 truce with the FARC Marxist rebels that ended five decades of conflict shifted priorities for many voters in the Andean country of nearly 50 million people. Inequality and corruption replaced security as the top issues for many, creating opportunities for the left.

Opinion polls show Petro in second place for Sunday’s first-round election, trailing right-winger Ivan Duque by around 12 points.

Though he may not win the race to replace President Juan Manuel Santos, Petro’s radical ideas are proving popular with many voters in Colombia, which is traditionally conservative on social issues and has deep economic divides.

“We’re not saying we should take land from the rich landowners: we’re inviting them to make it productive, to create jobs, to improve the conditions of the people who work there,” said Margarita Velosa, a 52-year-old university professor in Bogota who plans to vote for Petro.

Though Petro says his government would buy only unproductive land - rejecting charges by opponents that he would expropriate property - Ardila Lulle’s sugar company Incauca has 44,900 hectares (111,000 acres) planted with sugarcane, 76 percent of which is rented from other owners, according to its website.

ANGER AT STATUS QUO

Backing for Colombia’s left has simmered for years, though it failed to translate into victories at presidential elections, held every four years.

Petro was elected mayor of Bogota in 2011 but his term was marred by a trash-collection scandal that saw him temporarily dismissed.

The fiery populist told Reuters in a recent interview that elites’ control of politics has blocked ordinary Colombians from wealth and “impeded the construction of the nation.”

While the left remains diverse - encompassing former guerrillas and broadly progressive technocrats - Petro’s success may herald an opportunity for a stronger showing in future elections.

“Support for Petro is indicative of a growing populist dissatisfaction with the status quo,” said Sergio Guzman, Control Risks’ lead analyst for Colombia, who said voters are tired of inequality and corruption.

“Unless elites are able to address those issues, the frustration will likely persist well into 2022 and maybe even 2026.”

Both Santos and his right-wing predecessor Alvaro Uribe served two terms, pursuing military offensives against the FARC that forced the group to the negotiating table and led to the 2016 accord.

The left’s best chance for growth may lie with younger voters, who are less likely to have memories of the war.

Many of them are frustrated by mainstream parties after years of corruption scandals, accusations of deals with criminal elements and a failure to tackle inequality.

“There’s a lack of credibility for the political class,” said veterinary student Emanuel Pena, 25. “That makes you think that a shift toward the left - even if it’s not radical - is necessary and very possible.”

The left’s biggest challenge may come from within. In-fighting between parties has stymied coalitions and one well-known joke mocks the left as “reunida, no unida” - holding meetings, but never united.

More business-friendly, left-leaning candidates like Sergio Fajardo, who is in third place in opinion polls, have refused to join forces with the often-polemic Petro. It is unclear whether Fajardo and other more centrist leaders would back Petro if he makes it to a June second-round vote.

“If the left wants to win in 2022, they have to agree now on a united platform, a clear leadership structure and a disciplined message,” said Guzman of Control Risks. “Up to now, it has been more like an orchestra of soloists where every candidate has their individual issues.”

VENEZUELA FEAR

Growing success in local elections may be the key to building support, said Oscar Palma, political science professor at Rosario University in Bogota.

“Independent of Petro, independent of the presidential election, even independent of the FARC peace deal, we have seen a rising trend for the left,” he said. “That’s a process that could keep growing.”

The populist left has been ascendant before - and was met with violence. Liberal presidential candidate Jorge Eliecer Gaitan - a famed orator who railed against inequality - was assassinated in 1948 in an incident that sparked 10 years of violence and inspired rebel groups like the FARC.

The first FARC attempt to found a political party, called the Patriotic Union, resulted in the assassinations of some 5,000 party members by right-wing paramilitaries in the 1980s.

In other Latin American countries, such as El Salvador and Nicaragua, rebel groups have won power at the ballot box. However, a party set up by the FARC leadership - some of whom will likely face war crimes tribunals - received negligible votes in March’s legislative elections.

Many Colombians associate leftist parties with armed insurgents, especially with ex-rebels like Petro running. The M19 demobilized in 1990 and has had success integrating into mainstream politics.

“We’ve still not gotten over the idea that left means armed guerrillas,” said Palma.

Opposition to the FARC accord, which detractors saw as too lenient on the former guerrillas, remains a vote-winner for the right and Duque has promised to modify the deal if he wins office. Criminal gangs have expanded into areas once occupied by the rebels, allowing Duque to tap into fears that the peace process has made things worse.

The spectacle of neighboring Venezuela sinking into deep economic crisis under a Socialist government has also allowed him to argue that a leftist victory would spell disaster.

Right wing politicians say Petro represents Castrochavismo - a portmanteau reference to the late leaders of Cuba and Venezuela, Fidel Castro and Hugo Chavez.

More than half a million Venezuelans have arrived in Colombia, many in desperate need of food, housing and medical care - stoking anti-leftist fears.

“Colombia isn’t prepared to become a socialist or communist society, which would lead us to the same chaos that Venezuela is seeing,” said Jesus Lopez, 54, sporting a Duque T-shirt before a rally in Choco province.

Graphic on Latin American elections here.