Poisoning the well refers to the practice of presenting embarrassing information about an opponent, discrediting the opponent and, by extension, discrediting their message as well.
Is there a name for the variation I describe below?
Imagine a person we'll call X. X has impressive credentials (a science degree, lots of experience, etc.) and is outspoken on the issue of climate change. He's most closely associated with a theory that a big percentage of amphibian species will be extinct by the year 2050.
Now imagine some propagandists who recruit a really sleazy, bizarre individual (Z) to parrot X's message. It's the same message, but the messenger has become wholly disgusting, making the message look kooky as well.
Would you just call this "a variation of poisoning the well," or is there a specific name for it?