It’s pretty easy — it’s because he’s the most forceful with actual liberal policies.
He’s not trying to pre-negotiate himself out of making a forceful argument, he’s not trying to feel out what the right balance is — he’s going to push, and push, and push — and yes, he’s absolutely going to have to give in on some important points as he goes, but he’s never going to do it until he absolutely has to, and he’s going to be damned sure to get some longer-term concessions in exchange for every delay forced on something.
That’s not what I get from the other candidates.
And here’s the thing — I’d be out-and-out delighted to change my frontrunner the second any other candidate shows themselves a better player at that same game.
Because that’s the other secondary benefit to having him as the complete frontrunner now — he pushes the other candidates to grow some spine for speaking for their causes, to start fighting from a position of conviction, rather than acting like scavengers wary about reaching for meat from the Republicans.
I’m completely fine if he ends up losing — but I still see him as the best option for representing all the things I care about with someone in that seat.
If you prefer another candidate — excellent — but if you have any chance, ask them to be a lot more forceful about the issues they care about if they want to compete with Bernie, and I’ll be absolutely fine with them beating him when it comes to us ending up with a better candidate for arguing for our causes in front of a general audience!