From his linked article...
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Luis Guillermo Solis, a center-left former Costa Rican president, said Lopez Obrador's determination to clamor for an inclusive discussion showed off his anti-imperialist credentials, striking a tone with centuries of resonance in the region.
"The easiest way to do it is to symbolically fight with the United States," Solis said. "It's a well-known play in our neighborhood."
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"The summit aims to promote democratic unity, but the dispute exposed divisions between Washington and governments sympathetic to Cuban President Miguel Diaz-Canel, Nicaragua's Daniel Ortega and Venezuela's Nicolas Maduro, self-styled leftists who have long been reviled by the U.S. foreign policy establishment."
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The controversy risks overshadowing Washington's desire to prevent democratic backsliding in the region, said John Feeley, a retired U.S. ambassador and veteran Latin America diplomat who helped organize previous regional summits.
Feeley also flagged concerns about Brazil's far-right President Jair Bolsonaro undermining confidence in his country's October election and Salvadoran President Nayib Bukele's push to seek re-election despite constitutional term limits.
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IMO, Mexico's President understands the importance of this meeting and given all the shade still being thrown at Mexico by the U.S. recently (think Trump), he's going to leverage any opportunity he can to level the playing field.