McALLEN, Tex. — The former president of Mexico was accused of taking a $100 million bribe from El Chapo. A former sheriff in South Texas took far less from El Gallo — about $100,000.

El Gallo — Tomas Reyes Gonzalez, a drug trafficker now in federal prison — supplied the cash to the former Hidalgo County sheriff, Guadalupe Trevino, for his re-election campaign. Another former Hidalgo County sheriff took bribes to allow a convicted drug dealer to have conjugal visits at the county jail, including in the jail library and in the sheriff’s private office. Yet another former sheriff in neighboring Cameron County protected and assisted cocaine dealers, and is now Federal Inmate No. 51689-179.

The corruption that took down those three border sheriffs in 1994, 2005 and 2014 continues today. Next month, the former police chief in the town of La Joya is scheduled to go on trial, after he was indicted on drug charges and accused by federal authorities of helping a drug-trafficking organization transport narcotics while working as a police sergeant in Progreso, Tex.

The much-watched trial of the Mexican drug lord known as El Chapo — whose real name is Joaquín Guzmán Loera and who was convicted last week in a New York courtroom — shed light on the hold that drug traffickers and their money have on the police and politicians in Mexico. One witness at Mr. Guzmán’s trial testified that the Mexican president had taken a $100 million bribe in exchange for calling off a nationwide manhunt for the drug kingpin.