He literally lies about Lenin to convince people to vote for democrats. That is not a pipeline to the left. That is diverting people who were heading left towards his friends in the democratic party. The fact he screams at anyone who tries to point out that he is misrepresenting Lenin makes it clear this is a deliberate strategy, I imagine this is because if he wasn't serving the democrats he would lose access to them.
He is an active, deliberate impediment to the left.