Sneaking in Connotations
Wow, I've been calling this "Argument by Insinuation." It's certainly in widespread use and deserves a name.
I note that the smuggled connotations usually aren't emotionally neutral. Smuggling in "negative connotations" rather than just connotations. It's similar to ad hominem, but aimed at your opponent's position rather than at their person. Does applying negative labels sway an audience more powerfully than revealing flaws in an argument? If so, then even more persuasive is to employ subtle smears: smuggled connotations.
Also, perhaps the above example would be clearer if applied to concepts rather than people: remove any conflation with group stereotyping or race bigotry.