SAN SALVADOR — María de los Angeles Mena Alvarado knelt at the tomb of the slain archbishop and wept.

She had come to the crypt of the city’s cathedral to pray for a cure for the diabetes that was threatening her eyesight and weakening her kidneys. “I feel that, yes, he can perform a miracle,” said Ms. Mena, 62.

Thirty-five years after Óscar Romero, the Roman Catholic archbishop of San Salvador, was assassinated with a single bullet as he said Mass in a modest chapel here, this small country is celebrating his beatification on Saturday, the final step before sainthood.

For many here and in the rest of Latin America, though, Archbishop Romero is already a saint.

His tireless advocacy for the poor resonates deeply in a region where the gulf between those with riches and those without remains vast. He was the champion of impoverished Salvadorans, his homilies and radio broadcasts giving voice to their struggles. And as political violence battered the country and death squads killed any activist who challenged the existing order, the archbishop was defiant.