Pelosi privately told Biden polls show he cannot win and will take down the House; Biden responded with defensiveness

For all the vaguely bigoted caricatures of him as the quintessential grumpy old (Jewish) man from Brooklyn, Bernie's biggest problem was always that he's far too nice to people who stab him in the back (and front) and makes up all sorts of heinous things about him.

Classic examples from 2016 is when Hillary said that Bernie didn't have "real grandchildren" and he said nothing, or when he shot himself in the foot politically by telling the truth that "people are sick and tired of hearing about the damn emails" while she gave her most manically gleeful witch cackle.