Ehhhh...
http://www.gallup.com/poll/180440/new-record-political-independents.aspx
The split is close and usually favors Democrats. I'm sure you'll proceed to speculate that democratic leaning independents are center-left but don't feel at home with the party for some reason because that would fit nicely in to the narrative you'd like to spin... But, I think there's a healthy amount of progressives out there who identify as independent because they're tired of their votes being held hostage by Democrats because "at least we're not Republicans."
Either way, kirblar's line of thinking is hardly less speculative than current GE polling. Are we arguing that Bernie is polling better with independents because they don't know how much of an evil socialist he is yet? Or because they want to stick it to Hillary (then they'll magically side with her when it matters, I'm sure).
The anti-establishment sentiment is real, guys. Stop trying to shove this race into your convenient little "Bush v. Clinton 2: Electric Boogaloo" boxes.