And, again, Sanders is not Obama. They're not even comparable. I know a lot of Sanders fans really, really, really want them to be...but they're not. Not even close.
And thank heavens for that . Seriously though, as I wrote, it's precisely because Bernie has thoroughly demonstrated that he isn't just a "slick operator", that I think Bernie has the potential to far eclipse what Obama achieved, given the competition, especially, on the GOP front (i.e. I respectfuly, but wholeheartedly, reject your premise).
I'll tell you one thing, despite being the wise old age of 74, he seems to have boundless energy, and has possibly already exceeded the speaking engagements of Obama, in the 08 primary (purely based on variety of YT videos I see), or at least, exceeded the count, at this point in the campaign. As I mentioned previously, he totally smashed Obama's attendance record, for a primary event.
P.S. I updated my original post to mention one of the other nice union "gets" he received: the 185k strong, National Nurses United union, as covered in the 6 Reasons Why the Nurses Union Endorsed Bernie Sanders Over Hillary Clinton, Ecowatch article.