Just an inexplicably horrible campaign, all-around. The window is so damned tight, that you can't afford to set out two cycles when they're begging you to run, as he has done.
A Clinton caucuser tried to convince an undecided 88 year old caucused by saying sanders is too old to be president. D'oh
Probably, but he is going to be formidable for her in other areas of the country. Well, maybe not formidable, but a nuisance.