This tactic consists in presenting two or more different concepts together in the same context over and over again, so that an untrained audience is slowly and unconsciously led to believe there is little difference between the two, or that they are even the same thing.
This tactic is used to prevent people from considering "inconvenient" topics or ideas: by repeatedly presenting them in association with other ones that are conventionally agreed to be wither evil or stupid, people can be manipulated to reject the former together with the latter. In the same way, it can also be used for the opposite purpose, i.e.: to led people to accept harmful (for them) positions or ideas by associating them with universally agreed positive values.
This works better if the intended association is not explicitly stated but merely implied, since in this way it is easier for the intended message to bypass rational scrutiny.
The most blatant example of the use of this tactic by the mass-media can be found in the way they constantly mention several alternative/critical theories with absolutely no relationship to one another (conspiracy theories, flat Earth, no-vax, etc.) all at once in a "bundle" style, and always being careful to include both serious and easily disproven ones; the purpose is to subconsciously train people to think that there is no difference between them, so they can all be dismissed in block together with the blatantly fallacious ones.
The opposite variant of the association tactic; it consists in repeatedly presenting two concepts as fundamentally opposed to each other, usually through a "X versus Y", "X instead of Y", "the X side and the Y side" style, when there's no inherent opposition between the two, or even if they are strictly related. This variant can be used for the purpose of forcing people to "choose a side" between two potentially useful and empowering ideas, with the inevitable effect of rejecting one of them and keep them from achieving a complete awareness or emancipation, regardless of which "side" they choose.
The most blatant example of the use of this tactic by the mass-media can be found in how alterantive/critical theories are constantly contrasted against the "scientific" ones; in mainstream articles employing this tactic there's always a "scientific" side (which is always the one supported by the establishment) pitted against an alternative/critical side, with the obvious implication that the latter is not scientific; the purpose is to subconsciously train people to think that criticism of the establishment is incompatible with the scientific method, and therefore if they choose one they must reject the other.