Bernie is not a Democratic Presidential candidate. His role is protecting Mrs. Bill's left flank.
The Clintons couldn't have invented a better way to suck the oxygen away from, for example, an Elizabeth Warren.
Bernie is triangulation raised to the next level. An old, white, crazy-uncle-in-the-attic - who isn't even a Democrat - from a electoral vote poor State who floats all the socialist utopian canards: He makes Hillary look presidential by comparison. He lets her selectively navigate the memes that poll well with the economically ignorant.
You can't yet run left of Bernie in this country and win, but he defends a vast space to Hillary's left. They'll have to get through him to get to her.
Bernie proved he knows his place last night when, on behalf of all Americans, he apologized to Mrs. Bill for inquiries into her obfuscation of corrupt co-ordination between the Department of State and the Clinton Foundation, and for her flippant disregard for basic national security considerations: "For convenience." She accepted the apology. He accepted a reported $1.4 million in donations for his helpfulness.
You have to scroll down slightly for this clip (the first of two), to get the full-frontal cackling, bobble-head experience (watch Mrs. Bill, just listen to Bernie).