It was just before midnight when Enrique Peña Nieto declared victory as the newly elected president of Mexico. Peña Nieto was a lawyer and a millionaire, from a family of mayors and governors. His wife was a telenovela star. He beamed as he was showered with red, green, and white confetti at the Mexico City headquarters of the Institutional Revolutionary Party, or PRI, which had ruled for more than 70 years before being forced out in 2000. Returning the party to power on that night in July 2012, Peña Nieto vowed to tame drug violence, fight corruption, and open a more transparent era in Mexican politics.

Two thousand miles away, in an apartment in Bogotá's upscale Chicó Navarra neighborhood, Andrés Sepúlveda sat before six computer screens....