This seems to be a language drift worth nipping in the bud. It's not "fake". It's a lie. When something purports to be something it's not, "fake" is an adjective describing that thing. "Lie" is the adjective that describes the claim.
If you tweet that you are Man of the Year 2020, you are fake, a phony. The tweet, on the other hand, is simply a lie.
There is overlap, but the distinction is that "fake" things contain implicit lies about their nature.
Your example, a correctly attributed but false announcement about yourself, is not itself "fake" in any way - it's just a lie. There's no question over what it is - an assertion made by you.
But the original example:
"You just need to take a picture of X candidate, stick a made up quote beneath them, and put it on Facebook...
...creeps into "fake" territory because the image is an object with an implicit lie about its origins and motivation. The implicit lie - "I was created in order to raise awareness of a disturbing truth about candidate X" - is distinct from the explicit lie (candidate X said <thing>). Hence the superficially superfluous act of putting the text on a picture, instead of just tweeting "candidate X said <thing>".
The distinction is even more stark with the followup addition: "the fake-ness is even more effective, if the said candidate is the originator and controls the narrative." Here the explicit lie remains identical, but the implicit lie deepens considerably ("look at the fibs the crazy opposition is spreading around").
If you tweet that you are Man of the Year 2020, you are fake, a phony. The tweet, on the other hand, is simply a lie.