Admittedly so by her own supporters.

Trump's win was a combination of him rallying his own base and apathetic democrat voters assuming there was no chance he was going to win anyway and staying home instead of voting. With that knowledge in hindsight, a lot of people are not going to be making the same mistake in November and are ready vote for whoever the dem on the ballot is, regardless of whether s/he was their first/second/third choice.

And while Bernie himself isn't unlikable, at least not to me, I can easily see people not voting for him based on how annoying his vocal (though seemingly smaller than we thought judging by these results) supporters can often be.