Nobody cares about the VPs. People sometimes claim that a VP choice influenced their decision, but anyone who says so is lying to you and just presenting a post hoc justification for a decision that was already made, and made on (most likely) much more trivial factors. Of course, people do not like to betray the fact that they aren't terribly sophisticated in their decision making, so they'll come up with all sorts of post hoc justifications to pretend like they were analyzing things during the campaign.
Any Progressive voter who stayed home because they were upset that the VP, whose only role in dictating policy is serving as a tie-breaker in the Senate, was insufficiently progressive would have found some other dumb reason to not vote for her even if she did choose a "progressive" VP.
I don't think people make a decision based on the VP specifically, but they do based on what the VP represents. If Clinton had selected say, Warren or Sanders, that would be a signal that she was going to be running an administration friendly to economic populist/progressive/leftist policies. Picking Kaine represents more generic Democratic business as usual.
True in many cases but I don't think this is applicable here.
If you chose a progressive to balance the ticket, there are two choices: Bernie, or not Bernie.
After the scorched Earth insurgent campaign Sanders ran between March and June, there's no reason to pick him as a VP. He'd easily overshadow Clinton and had the potential take control of the message entirely out of her hands. From the Clinton staff's perspective, there is little upside to Clinton doing this.
For a non-progressive pick like Elizabeth Warren, that argument maybe made sense in 2017 but in 2019 it's pretty obvious that a large degree of 2016 Bernie voters were not pro-Bernie/progressive per se but either incredibly distrustful of the Democratic Party establishment or harboring a visceral hatred of Clinton. The fact that right now Joe Biden, of all people, is doing so well with so many of the same Demographics is very telling. There's very little reason to expect that choosing a non-Bernie candidate would have won back this demographic for very long.
Put another way: do you really think jfern would have supported Clinton if Elizabeth Warren was the VP in 2016? I highly doubt it.
