At least, running as a Democrat, he doesn't ciphon off votes, but rather competes among a pool of other candidates for the nomination. I get it. The party doesn't like him, so they'll use any means at their disposal to ensure that he doesn't become the candidate, but maybe they should be glad that he doesn't run as an Independent because then he WOULD ciphon votes. Give him a box on the ballot and he'll seize a notable block of the voters and, whatever the number, it'll be one that the Democrats will lament turning over so easily. Love him or hate him, their best bet is to let him caucus with the party, so they can contain the support behind him.

His biggest mistake was running as a democrat, now he wants to repeat it.

He is correct. Bernie has always been an independent.