Where the dynamics of 2016 is still relevant to me is it creates reservations about Sanders forming a broad coalition that he could take into the general - I’d argue that the 2008 Clinton machine was at least as formidable as the 2016 one yet Obama managed to translate some of the same early wins as Sanders far more effectively than Bernie did.Can't argue with your take on the 2016 dynamics, but I'm not sure how relevant that still is in 2020. The Clinton campaign was formidable in terms of funding, staff, resources, data, whereas the Sanders team essentially invented the campaign on the fly in 2016. They did not have the expertise or resources to take the South seriously, and it cost them the race.
But they are a far more professional organisation now, and they have been working non-stop for the past three years to build networks with minority voters. They also go much further than anyone else on issues that really matter to these communities, like criminal justice reform: https://www.vox.com/policy-and-poli...iminal-justice-reform-plan-mass-incarceration (cf. Harris!)
And so far, it is paying off. Sanders is the leading candidate among Latino voters, and second only to Biden among African-Americans (and I suspect Biden's lead here is very flimsy, like Clinton before Iowa in 2008). He is leading Harris 2-1 with Black voters. And he actually polls better among Black and Latino voters than he does among White voters (which your Politico chart also confirms): https://www.vox.com/2019/3/7/18216899/bernie-sanders-bro-base-polling-2020-president
Again, all of this is very fluid and not definitive proof of anything, but at the very least, recurring headlines like this are just wrong (at least in Sanders' case):
Sanders, Warren struggling to win support of black voters
Why don't more people know this? I have my theories... ; ) But suffice it to say that if, for instance, Buttigieg was leading with Latino voters, it is very hard to believe that this wouldn't have been much more aggressively brought to our attention.
Beyond that, Sanders has a huge, diverse, and very committed base, which is nationwide at level that so far only Warren can remotely match.
I am not sure if this has been posted here yet, but I think it matters far more than polls at this stage, because it measures the breadth and intensity of core support in a way that polls can't really depict: https://www.nytimes.com/interactive/2019/08/02/us/politics/2020-democratic-fundraising.html
Some candidates have clear regional bases, tapping into the donor networks that got them where they are now, but even in each of these cities or states, Sanders is almost invariably second. Donor support for Harris and Buttigieg (essentially an aspiring errand boy for the tech industry: https://newrepublic.com/article/154438/big-tech-want-buttigieg) is extremely confined to wealthy enclaves in the Bay and the Bos-Wash corridor, especially the posh bits of Connecticut. Biden can count on Delaware, and a handful of majority-black cities (whose elders are expecting him to win, and expecting favours down the road for their patronage). Only Sanders and Warren have a meaningful nationwide donor support base (though for now his is clearly more impressive), and the relatively small donations they collect are also very significant - it means a lot more to someone on $10/hour to give $27 than it does for someone who earns $250,000 to give $2700. Forget where I read this, but I think he also has more volunteers in Iowa than the rest of the field combined.
All of this makes Sanders overwhelmingly and by far the best choice in a general election: well-organised and passionate nationwide support, and appeal to broad range of otherwise unrelated constituencies, including non-voters and even many Republicans. And it makes him the candidate with the best chance of achieving the kind of decisive victory needed to actually implement the type of reforms that he and Warren recognise are necessary.
But you're right, it means nothing if he doesn't first win the primary.
And because he has achieved all of this precisely by challenging everything the Democratic Party actually stands for (ie: a corporate/elite patronage network which mirrors the GOP in seeking to contain everyday voters' economic expectations via permanent culture war), party elders see his many strengths not as an opportunity but as a threat.
There could be many reasons for that and I’m by no means ruling it out in 2020, just that I’m more in a “wait and see” mode, especially given that Biden is in my eyes a far weaker candidate than Clinton was at a similar stage and as you point out Sanders has far more experience/resources than he did in 2016.
The most obvious route to win back the presidency is through the Mid West which is probably Bernie’s strongest region - if in addition he could demonstrate in the primary robust Latino support that could turn some of the sun belt states like Arizona blue in the general whilst not turning off older suburban voters I’d gain more confidence in his nomination.
We shall see!
