Today, they in turn are being evicted or defeated, either electorally or through pressure from massive street protests . A new shift seems underway. But while there are significant differences in Latin America between the left and the right, or between neoliberalism and social democracy, the leeway for economic change is much more narrow than proponents of each side believe. More important, it is even smaller than what everyday Latin Americans expect.

The left has governed Chile for 24 of the last 29 years. The policies rejected today, through the clamor for less inequality and a more responsive political system, are largely those put in place by the Chilean center-left Concertación coalition. Chile is Latin America’s great success story, even if its citizens disbelieve this narrative, or reject it outright. True, Sebastián Piñera, the right-of-center president, is highly unpopular, but opposition, left-of-center parties, are equally unpopular.

Similarly, the economic crisis that led Argentines to bring back the Peronists, after four years under a pro-business president, is at least partly the making of those same Peronists, who were in office between 2002 and 2015 and have played an omnipresent role in the country’s disputes for power since 1945. Alberto Fernández, who was elected last month, may be the first Peronist leader who is neither corrupt nor a demagogue, but he will be governing in the company of Cristina Fernández de Kirchner, who was both, and a hard-left faction in Congress. Most importantly, though, Argentina owes $57 billion to the International Monetary Fund, and its new president will be forced to negotiate a new assistance package from the financial organization.

Mr. Morales had remained in power until now, partly thanks to the orthodox macroeconomic policies implemented since 2005, regardless of his rhetoric and anti-American grandstanding. His successful efforts to bring Bolivians out of poverty depended on high commodity prices; that era has ended. And Andrés Manuel López Obrador in Mexico is rapidly discovering that markets, budgetary constraints and the United States make many of his promises unviable. He detests neoliberalism, but desperately needs the United States Congress to ratify one of its icons: the 2.0 version of the North American Free Trade Agreement.

The incipient Latin American middle classes are the product of long-term, though modest, economic growth over the past quarter century. They have emerged from poverty, but feel that their life is not what it should be.