I’m sure this diary written by Markos himself will go well with some people there:

Bernie Sanders isn’t any more popular than ‘generic Democrat’:

We’ve been tracking the approval ratings of several key Democrats over the past several years at Civiqs. It’s not data we generally make public, but I’ll try to surface some of this when interesting stuff happens.

For example, it turns out that Bernie Sanders—protected by Republicans and Russians seeking to damage Hillary Clinton in 2015-16—now looks like a pretty generic Democrat once those protections are removed.

While it’s been a while since he’s been as popular with the general public as some seem to think (and it’s not just us seeing that decline in his numbers), his popularity took a real dive the day after the 2018 elections. Once he was seen as a presidential candidate, particularly in this crowded field with several great candidates, his numbers tanked.
A big chunk of that decline has come from independents (from 46-42 approvals the day before the election, to 35-50 today), not sure why that might be. What is probably easier to explain is his marked decline among Democrats:

(What he shows here isn’t opening in the work version of my browser.)

Now I know how people feel about Sanders, so I don’t think we need to rehash that since this isn’t about something he said or did. But, outside of the blogosphere, he’s not some mystical figure. We have to watch our own feedback loop, and make sure we don’t succumb to epistemic closure.