Turn the left against the center, turn it into a knife fight, scream about unfairness, insert the far right populist, and ta da: you've split the opposition while fanning enthusiasm on the right.

That some of the genuinely left people (lots of the endless attackers from the supposed left are actually agents of this strategy, like Jill Stein, etc.) don't seem to process this is just sign and symptom of how thoroughly defeated the left has been since the 1970s.

It's going to get a lot worse before it gets better, if it ever gets better in this era.