Less than a month after losing part of a lung, Pope Leo XIV set out this morning on one of the longest and most ambitious trips of his pontificate. Over the course of 11 days and 12 flights, Leo will travel from South America’s Southern Cone to the high Andes and the Amazon Rainforest. Much of the Catholic world will be focused on how its 71-year-old leader, just a few weeks removed from cancer surgery, bears the physical challenge that the trip presents. But perhaps the most important challenge he will face is political.

Catholic social teaching does not line up with the ideological commitments of either the left or the right. Yet the global rise of right-wing populism has determined many of the political battles that Leo will confront as pope, particularly over the next week and a half. The center-left recently scored a victory in Brazil, but most countries in Latin America are governed by right-wing or center-right leaders, many of them populist. These include two stops on the pope’s itinerary: Argentina and his adopted home of Peru, where he served as a missionary and bishop for about two decades.

Leo’s trip is an early test of how he’ll address the Church’s disagreements with the right-wing populist leaders ascendant not only in Latin America but also in Europe, the historic heartland of the Catholic Church. The emphasis he puts on either conciliation or confrontation could indicate how he’ll handle a geopolitical challenge that will shape his pontificate.

Crime might be the issue that best explains the rise of the South American right. Latin America and the Caribbean together have the world’s highest homicide rate, nearly four times the global average. About half of the population of this region feels unsafe walking alone at night, compared with about a quarter of people globally, according to a Gallup survey.

“There’s the violence associated with narcos fighting it out amongst themselves,” Cynthia Arnson, a fellow at the Latin America Studies Initiative at Johns Hopkins University, told me. “But then there’s the day-to-day robbery and extortion.”Arnson continued, “The right has very successfully capitalized on people’s legitimate fears and lived experience by proposing these super ironfist approaches.”The responses of right-wing leaders have created ample tension with the Church.

In Argentina, Catholic bishops opposed President Javier Milei’s plan to lower the age of criminal responsibility from 16 to 14. (Milei had previously suggested that 10 might be an appropriate cutoff.) The proposal became law in February, shortly after the murder of a teenager went viral. In El Salvador, President Nayib Bukele, the self-styled “world’s coolest dictator,” has employed mass arrests and declared an extended “state of exception.”These measures have curbed the country’s once-pervasive gang violence. But as local Catholic leaders and many other critics have pointed out, they have also flouted a range of human-rights laws.

Amid the national instability, Leo will visit a site with particular political resonance. In his former diocese of Chiclayo, the pope will stop at a chapel dedicated to one of Latin America’s most prominent victims of far-right violence: Saint Óscar Romero. In 1980, Romero was killed by right-wing death squads in El Salvador and later recognized as a martyr by the Church. Leo himself helped raise money for the chapel’s reconstruction.

Given his wide-ranging experience in Peru, he will likely try to balance his “sympathy for the need to promote citizen security” with a commitment to the rule of law, Matthew Carnes, a political-science professor at Santa Clara University who specializes in Latin America, told me.

American foreign policy under Donald Trump is bound up with the region’s emphasis on crime and the rightward shift of many governments there. According to U.S. officials, 18 countries in Latin America and the Caribbean, including Peru and Argentina, have joined Trump’s Shield of the Americas, a U.S.-led security coalition targeting drug trafficking and organized crime. The initiative is part of Washington’s regional strategy, dubbed the “Donroe Doctrine,” which aims to reestablish U.S. dominance in the Western Hemisphere.

Trump’s actions in the region have drawn scrutiny from the Church. Last year, Leo questioned the administration’s military buildup off the coast of Venezuela, where the United States struck boats suspected of being used for drug trafficking. In January, a U.S. military operation toppled President Nicolás Maduro: The pope insisted that Venezuela’s sovereignty and constitution be respected.

Leo has also clashed with the White House over Trump’s hard-line immigration policies, which resemble those of some Latin American leaders. In Peru, for example, Fujimori has pledged to expel undocumented immigrants, many of whom have come from Venezuela, and to use the military to police her country’s borders. Leo may use his visit to reiterate his advocacy for migrants, a consistent theme of his pontificate that he has stressed on other international trips this year, including in Spain and France.

Another common feature of right-wing governments in the region is their push for a lean state, in part through cuts to social services. No leader is more emblematic of this effort than Milei, who campaigned with a chain saw to illustrate his zeal for budget slashing. Argentina’s Catholic bishops have criticized his government’s austerity policies, including cuts affecting a care home for the disabled that Leo is scheduled to visit. That stop itself could be seen as a political critique from the pope, who has called the welfare state “a genuine universal right.”

Likewise, his scheduled meeting with trade unionists, business leaders, and representatives of social movements in Buenos Aires will be a natural setting for him to defend workers’ rights, a key principle of the social teaching of his namesake, Pope Leo XIII.

As a presidential candidate, Milei criticized and even insulted Pope Francis, once accusing his fellow Argentine of having an “affinity for murderous Communists.”But the two held an apparently friendly meeting at the Vatican in February 2024, after Milei’s victory. Francis never visited his native land as pontiff, perhaps out of a reluctance to become embroiled in domestic politics. As a young priest, Francis had ties to the movement founded by Argentina’s longtime strongman Juan Perón, whose political heirs make up the principal opposition to the current government. Leo, by contrast, is not seen as aligned with any one movement in Argentina and will be freer to speak, Carnes said.

The odd country out on Leo’s itinerary is Uruguay, which has one of the region’s few left-leaning governments. The pope may highlight the country’s robust welfare system as a model for its neighbors, Michael Shifter, a senior fellow at the Inter-American Dialogue, a Washington-based think tank, told me. But Leo will also have right-coded criticisms to make in Uruguay, one of Latin America’s most secular societies, where less than half of the population identifies with an organized religion. Last year, the country legalized euthanasia, which may prompt Leo to echo the forceful statements he recently made in France on the same issue.

But there are also reasons to think that Leo may take a more restrained approach during the trip. As with much of the West, Latin America is growing more politically polarized, analysts told me. Leo, who has made unity a watchword of his pontificate, is likely “to stress the importance of reconciliation, of dialogue, of trying to overcome some of the divisions that we see in many countries,” Shifter said. “There really is no other leader in Latin America today who could do that.”Leo certainly commands unusual credibility among South Americans. The question is whether that credibility will be enough for him to draw a continent together while challenging the ideology that dominates it.