In the public eye, Conrado Cantu had it all. The former Cameron County sheriff was often described as charismatic, a man with a firm handshake and a popular catchphrase “Animo” — meaning cheer and encouragement — that became synonymous with his own name. He had politicians by his side, voters on their feet, a badge and a fleet of law enforcement officials at the ready. But the brass badge that adorned his chest was used to shield political allies and drug traffickers, federal investigators are alleging. It helped the former lawman collect a percentage of drug profits and shake down...