For sure there is still sexism. What are you thinking numerically when using the word vast? And for the purposes of electing a democrat in 2020 (something you and I agree on), we can limit ourselves to swing voters or apathetic voters. Most voters who come out every year and vote their party will vote for a woman and that is even true with the Republicans I’d say (too bad Elizabeth Dole, Christine Todd Whitman, or some other woman didn’t win the R nomination in the past so I could test this assertion). So of the wishy-washy voters who would tend to vote D if there is a decent man opposing Trump in the general, do you think 20% would stay at home/vote third party or worse, switch to Trump if a woman were running? I think the number of votes that Clinton got (and she didn’t get mine, but she would have if I didn’t live in CA) shows that the sexism problem isn’t vast, but I agree it could be significant (say 2-5% of these voters) and even 0.1% of the total vote can swing an election.
I have my reasons for preferring Sanders to Warren, but between Gabbard and Sanders, I actually preferred the woman (until recently where I’m not happy with her comments on private health insurance compared to Sanders and I don’t think she is going to make the next debate anyway). Warren has plenty of things different than Sanders that absolute conclusions on these polls are going to be difficult.