For the bulk of his tenure, New York City mayor Bill de Blasio has been dogged by rumors that he and his wife consume marijuana with some frequency. Yesterday, at a press conference in Brooklyn, he told a Daily Caller reporter that “I haven’t smoked marijuana since I was at NYU” and denied he ever smoked weed at Gracie Mansion, the official residence of the mayor. We’ve asked about these rumors ourselves. It’s worth highlighting, however, who exactly is spreading them: The mayor’s security detail and their colleagues in the New York City Police Department.

Over the past year, we’ve heard from a broad array of sources—Democrats and Republicans; aides and operatives; journalists and flacks—about the mayor’s marijuana habit. For a rumor, the details have remained fairly consistent. The main four are:

As Public Advocate, de Blasio and his wife, Chirlane McCray, liked to smoke in either their Park Slope rowhouse or a secluded section of Prospect Park; De Blasio’s unexplained decision to forgo the Public Advocate’s assigned N.Y.P.D. security detail was based on his wife’s fear that they would be caught smoking; After de Blasio became mayor, the couple began smoking at Gracie Mansion; Both the Mayor and First Lady remain suspicious that the N.Y.P.D. security detail assigned to the Mayor’s Office have leaked information about their activities and whereabouts to the press. (From a recent Politico piece: “In 2013 de Blasio’s team was even convinced that members of his police detail were eavesdropping on his private conversations in his city-assigned car.”)

Another consistent detail about these rumors is their source. Almost every person we spoke with indicated that these stories came from cops assigned to protect the mayor, and were later promulgated by their colleagues in the police department. We’re also told that the police unions have played a significant role in this whisper campaign; the president of the Sergeants Benevolent Association, Ed Mullins, came up in more than one of these conversations.

The fact that these rumors are coming from cops—whose racist stop-and-frisk policy de Blasio railed against during the mayoral election—does not necessarily make them untrue, or unworthy of more reporting. It would be indisputably newsworthy if the mayor of New York City smokes marijuana while the city he oversees continues to arrest people of color over small quantities of cannabis. It would be indisputably newsworthy, too, if he had repeatedly misled the public about his consumption of marijuana.

It is equally obvious, however, that N.Y.P.D. officials want to undermine and embarrass the de Blasio administration in any way they can—such as spreading rumors about the mayor’s weed habit—in order to deflect and distract the public from their department’s well-documented brutality. So when you hear about de Blasio smoking pot, keep in mind who wants you to hear about it, and why.