What’s the evidence for supporting Clinton in 2016 hurting his credibility among non-voters? Non-voters are almost by definition a diverse cohort, and their only consistent feature is a personal disengagement from politics. I don’t think many of them, presented with the appeal that Bernie Sanders is the candidate trying to take on Wall Street and change the Democratic party from the inside, would respond with “ah, but didn’t he concede in 2016 and throw his weight behind Clinton? I think I will continue to not vote.”

To me that theory sounds like the magical thinking of disempowered radicals, that we actually already have popular support, and we simply need to call on the masses to join us with a strong enough voice.