MEXICO CITY—The arrest on corruption charges of the head of Mexico's teachers union was widely seen Wednesday as a double win for President Enrique Peña Nieto, striking a blow against a controversial political figure and reasserting state authority over special interests.

Elba Esther Gordillo, one of the country's most powerful political figures of the past two decades, appeared in a televised courtroom inside a grim Mexico City prison to hear charges of money laundering and organized crime read out against her.

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