For eight years, Sepúlveda, now 31, says he traveled the continent rigging major political campaigns. With a budget of $600,000, the Peña Nieto job was by far his most complex. He led a team of hackers that stole campaign strategies, manipulated social media to create false waves of enthusiasm and derision, and installed spyware in opposition offices, all to help Peña Nieto, a right-of-center candidate, eke out a victory. ... Sepúlveda’s career began in 2005, and his first jobs were small—mostly defacing campaign websites and breaking into opponents’ donor databases. Within a few years he was assembling teams that spied, stole, and smeared on behalf of presidential campaigns across Latin America. He wasn’t cheap, but his services were extensive. For $12,000 a month, a customer hired a crew that could hack smartphones, spoof and clone Web pages, and send mass e-mails and texts. The premium package, at $20,000 a month, also included a full range of digital interception, attack, decryption, and defense. The jobs were carefully laundered through layers of middlemen and consultants. Sepúlveda says many of the candidates he helped might not even have known about his role; he says he met only a few. ... His teams worked on presidential elections in Nicaragua, Panama, Honduras, El Salvador, Colombia, Mexico, Costa Rica, Guatemala, and Venezuela. ... He’s serving 10 years in prison for charges including use of malicious software, conspiracy to commit crime, violation of personal data, and espionage, related to hacking during Colombia’s 2014 presidential election.