No presidential election is going to swing 60-40, but I hate to say it: I think Trump beats Sanders in a general. From my perspective, there's way more loony far-right idiots than there are loony far-left idiots, and they're much more motivated to not only vote, but to organize, to rally, to work phone banks, to arrange transportation.
I think the country is more leftward than the GOP candidates claim, but I also think most people want to be entertained and the Presidential race has become another sport. If its Donald v Bernie, Donald unleashes zinger after zinger, Bernie struggles to keep up, and the right cheers for their Alpha Male candidate.
Don't forget that Trump has unlimited money. This is very significant. He will never have to cut resources in one state in order to shore up another state. He will never have to tie together coalitions of competing interests. He'll never have to waste time holding fundraising parties. Bernie will still have to do all of that.
If Hillary is the candidate, I think she can take ahold of the narrative and defeat Trump. But I feel like if he's under fire, Bernie's persona will evolve into