Warren is a prime contender for a "Top 10 anime betrayals" compilation at this point.
Back when she was at her peak and was thought to overtake Bernie and maybe even become the frontrunner, the general sense I got from Bernie supporters (including myself) was that they would gladly support her as a second choice. Yeah, she was a capitalist, and definitely more moderate than Bernie, but she was clearly a viable alternative for lefties like myself should Bernie falter - the only alternative, really. I can't speak for anybody else with certainty, but if Bernie and Warren's results were reversed, I would definitely be advocating for Bernie to drop out either now or after ST and endorse Warren. And if he decided to keep running to either block Warren or bet on a contested convention like she's doing, I'd call him out hard.
I had the impression that the reverse wasn't as true for a chunk of the Warren base, though it's just my perception, but Warren herself always made it sound like she would clearly be on Bernie's side when push came to shove. That he and she were natural allies from the get-go, and that whoever got the edge would get the other's support for the sake a pushing a truly progressive agenda. That their main goal would be to make the US a better place to live. After all, Bernie did encourage her to run in 2016. I mean, look at this:
But nope. At this point, one wonders if her failings are still mostly due to bad campaigning and bad advice from her staff, or if she always had it in her to play the career game like most politicians, country be damned. I used to be in the former camp and sweep her mistakes under the rug of political incompetence, but I'm not so sure anymore.
A disappointment through and through.
[EDIT] That poll someone posted below shows, unlike my perception, that Warren supporters still would largely support Sanders if she dropped out. It doesn't change my overall message, but let's be accurate.