It's difficult to say really, how many on the left are really aware of what they're doing and how many are just the useful idiots to be used by those that know. Even of those that are aware though, I wonder how many think that they will be able to be at or near the top in a Marxist system. While the stated principles of Marxism are equality for all, those not taken in by the fallacy of idealism and those who have experienced it first hand, know all too well that actually becomes a pyramid scheme. If the full efforts of the left ever reach fruition in the US then many who desired it will come to recognize and regret the reality too late. I have a difficult time trying to fathom how someone who does know, could possibly anticipate a personal gain.
A thought to ponder with regard to current proposals and efforts by the left is this; the Soviet Union collapsed beneath unsustainable spending. Most of that was more on military programs rather than social programs, of course, but still it was spending more than what they could take in. The other thing was that when it collapsed those who believed in the system did not simply go away or see and admit the inherent errors. I would imagine that a great many were left with a tremendous bitterness and resentment toward capitalism and the West for whom they blamed the collapse and whom were happy enough to take the credit. One might well imagine that those believers, many of which are now in our own systems, are eager to exact a revenge by compelling our governments to also spend themselves into collapse, although through social and domestic spending rather than defense? That is of course the Cloward-Piven strategy.
The most unfortunate thing is that it's almost certain that there won't be any neutral position to be held.