RIO DE JANEIRO — In the final weeks of 2021, Chile and Honduras voted decisively for leftist presidents to replace leaders on the right, extending a significant, multiyear shift across Latin America.

This year, leftist politicians are the favorites to win presidential elections in Colombia and Brazil, taking over from right-wing incumbents, which would put the left and center-left in power in the six largest economies in the region, stretching from Tijuana to Tierra del Fuego.

Economic suffering, widening inequality, fervent anti-incumbent sentiment and mismanagement of Covid-19 have all fueled a pendulum swing away from the center-right and right-wing leaders who were dominant a few years ago.

The left has promised more equitable distribution of wealth, better public services and vastly expanded social safety nets. But the region’s new leaders face serious economic constraints and legislative opposition that could restrict their ambitions, and restive voters who have been willing to punish whoever fails to deliver.

The left’s gains could buoy China and undermine the United States as they compete for regional influence, analysts say, with a new crop of Latin American leaders who are desperate for economic development and more open to Beijing’s global strategy of offering loans and infrastructure investment. The change could also make it harder for the United States to continue isolating authoritarian leftist regimes in Venezuela, Nicaragua and Cuba.

With rising inflation and stagnant economies, Latin America’s new leaders will find it hard to deliver real change on profound problems, said Pedro Mendes Loureiro, a professor of Latin American studies at the University of Cambridge. To some extent, he said, voters are “electing the left simply because it is the opposition at the moment.”

Poverty is at a 20-year high in a region where a short-lived commodities boom had enabled millions to ascend into the middle class after the turn of the century. Several nations now face double-digit unemployment, and more than 50 percent of workers in the region are employed in the informal sector.

Corruption scandals, dilapidated infrastructure and chronically underfunded health and education systems have eroded faith in leaders and public institutions.

Unlike the early 2000s, when leftists won critical presidencies in Latin America, the new officeholders are saddled by debt, lean budgets, scant access to credit and in many cases, vociferous opposition.

Eric Hershberg, the director of the Center for Latin American and Latino Studies at American University, said the left’s winning streak is born out of widespread indignation.

“This is really about lower-middle-class and working-class sectors saying, ‘Thirty years into democracy, and we still have to ride a decrepit bus for two hours to get to a bad health clinic,’” Mr. Hershberg said. He cited frustration, anger and “a generalized sense that elites have enriched themselves, been corrupt, have not been operating in the public interest.”

Covid has ravaged Latin America and devastated economies that were already precarious, but the region’s political tilt started before the pandemic.

The first milestone was the election in Mexico of Andrés Manuel López Obrador, who won the presidency by a landslide in July 2018. He declared during his election night address: “The state will cease being a committee at the service of a minority and it will represent all Mexicans, poor and rich.”

The next year, voters in Panama and Guatemala elected left-of-center governments, and Argentina’s Peronist movement made a stunning comeback despite its leaders’ legacy of corruption and economic mismanagement. President Alberto Fernández, a university professor, celebrated his triumph over a conservative incumbent by promising “to build the Argentina we deserve.”

In 2020, Luis Arce trounced conservative rivals to become president of Bolivia. He vowed to build on the legacy of the former leader Evo Morales, a socialist whose ouster the year before had briefly left the nation in the hands of a right-wing president.

Last April, Pedro Castillo, a provincial schoolteacher, shocked Peru’s political establishment by narrowly defeating the right-wing candidate Keiko Fujimori for the presidency. Mr. Castillo, a political newcomer, railed against elites and presented his life story — an educator who worked in a rural school without running water or a sewage system — as an embodiment of their failings.

In Honduras, Xiomara Castro, a socialist who proposed a system of universal basic income for poor families, handily beat a conservative rival in November to become president-elect.

The most recent win for the left came last month in Chile, where Gabriel Boric, a 35-year-old former student activist, beat a far-right rival by promising to raise taxes on the rich in order to offer more generous pensions and vastly expand social services.

The trend has not been universal. In the past three years, voters in El Salvador, Uruguay and Ecuador have moved their governments rightward. And in Mexico and Argentina last year, left-of-center parties lost ground in legislative elections, undercutting their presidents.

But on the whole, Evan Ellis, a professor of Latin American studies at the U.S. Army War College, said that in his memory there had never been a Latin America “as dominated by a combination of leftists and anti-U. S. populist leaders.”

“Across the region, leftist governments will be particularly willing to work with the Chinese on government-to-government contracts,” he said, and possibly “with respect to security collaboration as well as technology collaboration.”

Jennifer Pribble, a political science professor at the University of Richmond who studies Latin America, said the brutal toll of the pandemic in the region made leftist initiatives such as cash transfers and universal health care increasingly popular.

“Latin American voters now have a keener sense of what the state can do and of the importance of the state engaging in a redistributive effort and in providing public services,” she said. “That shapes these elections, and clearly the left can speak more directly to that than the right.”

In Colombia, where a presidential election is set for May, Gustavo Petro, a leftist former mayor of Bogotá who once belonged to an urban guerrilla group, has held a consistent lead in polls.

Sergio Guzmán, the director of Colombia Risk Analysis, a consulting firm, said Mr. Petro’s presidential aspirations became viable after most fighters from the FARC, a Marxist guerrilla group, laid down their weapons as part of a peace deal struck in 2016. The conflict long dominated Colombian politics, but no more.

“The issue now is the frustration, the class system, the stratification, the haves and have-nots,” he said.

Just before Christmas, Sonia Sierra, 50, stood outside the small coffee shop she runs in Bogotá’s main urban park. Her earnings had plummeted, she said, first amid the pandemic, and then when a community displaced by violence moved into the park.

Ms. Sierra said she was deep in debt after her husband was hospitalized with Covid. Finances are so tight, she recently let go her only employee, a young woman from Venezuela who earned just $7.50 a day.

“So much work and nothing to show for it,” Ms. Sierra she said, singing a verse from a song popular at Christmastime in Colombia. “I’m not crying, but yes, it hurts.”

In neighboring Brazil, rising poverty, inflation and a bungled response to the pandemic have made President Jair Bolsonaro, the far-right incumbent, an underdog in the vote set for October.

Former President Luiz Inácio Lula da Silva, a leftist firebrand who governed Brazil from 2003 to 2010, an era of remarkable prosperity, has built a 30 percentage point advantage over Mr. Bolsonaro in a head-to-head matchup, according to a recent poll.

Maurício Pimenta da Silva, 31, an assistant manager at a farming supplies store in the São Lourenço region of Rio de Janeiro state, said that he regretted voting for Mr. Bolsonaro in 2018, and that he intended to support Mr. da Silva.

“I thought Bolsonaro would improve our life in some aspects, but he didn’t,” said Mr. da Silva, a father of four who is no relation to the former president. “Everything is so expensive in the supermarkets, especially meat,” he added, prompting him to take a second job.

With voters facing so much upheaval, moderate candidates are gaining little traction, lamented Simone Tebet, a center-right senator in Brazil who plans to run for president.

“If you look at Brazil and Latin America, we are living in a relatively frightening cycle of extremes,” she said. “Radicalism and populism have taken over.”

Ernesto Londoño and Flávia Milhorance reported from Rio de Janeiro. Julie Turkewitz reported from Bogotá.