I am not really scared of Bernie as he doesn't have the House or Senate behind him, and so he will only be able to get done things they agree to. But I think Warren will replace him on the left, eventually.
The numbers for Trump vs all Dems look quite similar to those vs HRC, in the parts of the pre-election cycle where she was 10 points ahead.
There are more Dems. Marginal Dems are currently solidly blue. Marginal Republicans are demoralised because Trump is useless, but some haven't defected because the economy isn't broken yet. Trump fans are still in the grip of Fox News and can't be reasoned with. That's the way it was and remains.