The fact that Sanders gets considered "authentic" while many other candidates get tagged as "inauthentic" has more to do with double standards in how they're covered. Warren used to be a Republican and we hear about it constantly; Sanders used to advocate for the nationalization of most major industries (a policy he has since backed away from, at least in public) and we rarely hear a peep. Sanders gets asked the first candidate he ever voted for and says "Kennedy," a statement that conflicts with both the calendar (he was too young to vote for JFK, and wouldn't have had the opportunity to vote for RFK based on where he lived at the time) and his own past public statements about the first time he voted (around age 40). So far, it's gone relatively unnoticed. Elizabeth Warren refers to her father as a "maintenance man" when she previously said "janitor" (as if those jobs have never been combined), or Kamala Harris says she listened to Tupac in college, and we get dozens of articles and days' worth of "oh my god, can't this woman ever tell the truth?" If Bernie gets perceived as "more authentic," it has a lot to do with the way he skates by without much vetting while other candidates, women in particular, get every single word they utter dissected under an electron microscope.