LOS ANGELES — Colombia’s political sphere is on the verge of change, with the primary elections showing a leftist shift in one of Latin America’s most conservative societies. A former guerrilla group member, Gustavo Petro, is leading the polls in the presidential race. If he wins on June 19, he would become the first leftist president in the country’s history. 

Mr. Petro and his running mate, Francia Márquez, received 40 percent of the votes in Sunday’s six-candidate primary; he will face off against the conservative candidate, businessman Rodolfo Hernández, who won 28 percent.

The 62-year-old Mr. Petro is calling for a new economic model in Colombia. He aims to halt oil exportation, which would represent a break in the country’s long reliance on crude and coal exports. In addition, Mr. Petro wants to raise taxes for 4,000 of the wealthiest Colombians and has said he’s prepared to declare an “economic emergency.” 

During a presidential debate on March 14, candidates were asked about relations with Venezuela and its president, Nicolas Maduro. Mr. Petro replied: “If the theory is that with a dictatorship you can’t have diplomatic relations, and Venezuela is, why does this government have diplomatic relations with the United Arab Emirates, which is a dictatorship, perhaps worse?”

For decades, Colombia’s political spectrum has been dominated by a conservative political party, the Uribismo, founded by President Alvaro Uribe. The upcoming election could mark a big move to the left.

At the age of 17, Mr. Petro became a member of the 19th of April Movement, a guerrilla group that emerged in 1974 and is known as M-19. It terrorized the population until 1990. By 1985, with the number of active members reaching 2,000, it was the second-largest guerrilla group in the country, following the Revolutionary Armed Forces of Colombia, known as Farc.  

Some of the M-19’s most notorious acts included stealing one of Simon Bolivar’s swords from a museum, kidnapping the president of the Confederation of Workers of Colombia, Jose Mercado, and, during a cocktail party in the Dominican Republic’s embassy, taking hostage 14 ambassadors.

In 1991, the M-19 was demobilized and former members, including Mr. Petro, formed the political party M-19 Democratic Alliance. An associate professor of political science at Universidad de Los Andes in Bogotá, Felipe Botero Jaramillo, said he believes this was the start of the acceptance of the left in the country.

In 2002, Mr. Petro, then a member of the political movement Via Alterna, was elected to the Chamber of Representatives. In 2006, he became a senator as a member of the election coalition Independent Democratic Pole. He later resigned to participate in the 2010 presidential election, finishing fourth. 

Between 2012 and 2015, Mr. Petro was mayor of Bogotá. During his administration, homicide rates reached 20-year lows, as he prohibited the carrying of firearms. A number of new institutions, such as the LGBTI Citizenship Center, were inaugurated.

Last year, Mr. Petro declared that he would be running in the 2022 presidential elections. His popularity soared as the pandemic crushed the economy, leaving millions with lower incomes and many unable to afford food. His message of taxing the rich and promising a public sector job to anyone who is unemployed has made him popular among Colombians. 

However, Mr. Botero says that there are still those who fear the idea of a former member of the M-19 leading the country. He says those will support Mr. Hernández, a wealthy businessman and former mayor of Bucaramanga. 

Since the creation of the M-19 Democratic Alliance and the 2016 peace agreement with the Farc, the left has been gaining acceptance slowly. In two weeks Colombians will demonstrate how much change they want.