Which Democrats would be losing to Trump right now?

[Devout Centrist]

Webb would be losing because the base would loathe him.

Chafee would have had to run the best campaign in history to win, so he'd be leading. I think O'Malley would be ahead, but by less than Clinton.

Sanders would be ahead by 5-8 points.

[Devout Centrist]

Webb would be losing because the base would loathe him.

Where do you think the base will go? Stein? Trump? Ha.

Johnson, maybe some to Stein. Some won't vote, especially younger, more apathetic types.

[Devout Centrist]

Any Democrat with a pulse and without a corruption or sex scandal in their past would be ahead of Trump.  The fact that the race is even borderline competitive says a lot about Hillary Clinton.

Bottom line: Hillary, while highly experienced and competent, is a very flawed and distrusted candidate. Almost any other non-Trump GOP candidate (except Cruz, Carson, Bush or Gilmore) would be ahead of her right now.

I think you underestimate how polarized American politics are.