Also, just for fun, here's an old story from the NY Times about allegations about Sáenz while serving in the Zedillo administration, and how it drove a wedge between the US and Mexican governments. The same thing happened with regard to Manlio Fabio Beltrones a couple of years prior, and the subsequent history certainly seems to suggest that the Mexicans were right in dismissing the allegations, while the American officials pushing the stories were overzealous and credulous. I'm not as familiar with the allegations regarding Sáenz, but his recent record and this passage together seem to suggest that a similar dynamic was at play in his case.
Mexican officials said the allegations against Mr. Saenz came from half a dozen sources, including several drug traffickers. All offered second-hand information about his activities, or claimed ties to him that they could not prove. At least one failed a lie-detector test, the officials said.It's kind of ridiculous that despite the bolded section, the charges were given sufficient credence to spark a diplomatic row that wound up in the NY Times. For a Mexican drug trafficker, starting a whisper campaign against an honest official would not be a particularly complicated affair, so if officials in a position to act on those rumors are not endowed with much skepticism, this is what happens.