I'll grant that the use of "very" there is overstating it, I have a tendency to do that, but a number of people here have mentioned that a noticable amount of people in their orgs cite him as a factor in them starting to move left and organize. I didn't mean to imply that he's the end all be all of moving someone left. He tries to move people into spaces where other socialists pick these people up and keep moving them along and keep them engaged in the work. That, plus seemingly the entire mainstream media trying to paint him as a demon means he's not completely ineffectual. The political establishment is afraid of him to some degree, maybe if only because he's started to really lean in to promoting candidates.