Americas-MOAS

After years of watching his influence in Latin America slip away, Mr. Obama suddenly turned the tables this week by declaring a sweeping détente with Cuba, opening the way for a major repositioning of the United States in the region.

Washington’s isolation of Cuba has long been a defining fixture of Latin American politics, something that has united governments across the region, regardless of their ideologies. Even some of Washington’s close allies in the Americas have rallied to Cuba’s side.

“We never thought we would see this moment,” said Brazil’s president, Dilma Rousseff, a former Marxist guerrilla who chided the Obama administration last year over the National Security Agency’s surveillance of her and her top aides. She called the deal with Cuba “a moment which marks a change in civilization.”

“What has been proposed as solutions are like treating cancer with an aspirin,” said Juan Pardinas, a political analyst at the Mexican Institute for Competitiveness, a research group based here. “There is a kind of deafness on their part without recognizing the huge opportunity to change things in Mexico as a result of this crisis.”

“It is a historic breach here,” said Mauricio Merino, an analyst at CIDE, a Mexico City policy institute, and one of 80 intellectuals and representatives of watchdog groups who called on political leaders this week to jettison the proposal for a single special prosecutor and instead create an independent body to fight corruption at the highest levels. “The political class has the power, and they are trying to keep it.”

“The federal government has shown a very limited and inappropriate capability to react, and it hasn’t found a rhetoric and narrative that fits this moment of crisis,” he said. “It will be very hard for him to find it, since every discovery and confirmation of the students’ death only fuels the movement and empowers people to mobilize.”

Uruguayan voters elected Tabaré Vázquez as president on Sunday in a show of support for the leftist coalition that has governed the country over the last decade, presiding over robust economic growth and a pioneering set of socially liberal laws, including a state-controlled marijuana market.

The election came after a stretch in which Uruguay’s president, José Mujica, 79, a former guerrilla, raised the country’s profile with legislation that legalized abortion and same-sex marriage and created the marijuana market. He is set to leave office with high approval ratings.

Dr. Vázquez is more moderate than Mr. Mujica, having vetoed an abortion law during his first term as president. He has also expressed opposition to parts of the marijuana law, a position shared by many Uruguayans as broad skepticism persists over the project. Still, he has said that he would enforce the law.

The authorities in Venezuela charged a leading opposition politician on Wednesday with taking part in a plot to assassinate President Nicolás Maduro. The politician, María Corina Machado, was informed of the charge in a meeting with prosecutors but was not detained. The national prosecutor’s office said in a statement on its website that Ms. Machado was charged with conspiracy and that, if found guilty, she could be sentenced to eight to 16 years in prison.

Ms. Machado, who denies taking part in a plot, was a vocal supporter of widespread antigovernment protests this year. Another politician who supported the protests, Leopoldo López, was charged with promoting violence and has been imprisoned.

The State Department in Washington issued a statement saying, “We are deeply concerned by what appears to be the Venezuelan government’s continuing effort to intimidate its political opponents through abuse of the legal process.”