He's the candidate. A candidate that was supposed to attract Republican moderates. Go get them.
But having voters on your side who might otherwise vote Republican is badwrongeeeeviiilllll!!!

Oops, wait... that was just for Bernie.

Getting them means moving right.
Only if one thinks of politics as having only a single spectrum along which people take their positions. Another spectrum, with populism at one end and something we don't have a single name for at the other end (something like oligarchy or elitism or even just anti-populism), actually describes the situation better lately, and people whose positions are defined primarily on that spectrum exist on both the right and the left.
That's part of why the gloating corporatist Democrats' sneering derision about Bernie not winning in "his own party" are entirely bonko. It treats the internal machinations of the party as the easy part, when in fact, as he and his supporters knew and said all along, that was always going to be the hard part.
The Clinton/Obama administrations willfully neglected the interests of the left as a political ploy. A brinkmanship tactic that the left's only recourse is to allow a Republican to be elected.
Every time they trot out the brinksmanship and fear-mongering about how
this particular Republican candidate must be stopped and
this particular election is so uniquely important that we just can't let it go wrong
this particular time, and we can go back to debating what this party should stand for or who the bad apples are in this party some other time when the stakes aren't so uniquely high as they are just
this time... it makes me wonder when that time we're supposed to be waiting for, when it will finally be OK to dispute their
rightful dominance in the party, will ever arrive... because the Republicans somehow keep putting up opponents, and then the next time around it's the same thing again just like last time and the time before and so on. When are they telling us the Republicans will just sit one out or put up a candidate who's just fine to Democrats? Because I don't believe such a time will ever come, and if it's not about waiting for the right time, then it's just an excuse to never
ever be challenged, a modern-day divine right of kings.