History of the Bern
Pundits can tell you all the political blunders Bernie Sanders made to lose his lead over Biden, but:
I suspect that in historical memory a different story will prevail, one that centers around neither candidate but instead makes the coronavirus the crucial player in the Democratic drama.
In this story, the Biden consolidation will be a subplot in the drama of contagion, the story of an America slowly awakening to the scale and scope of the coronavirus threat, and his swift victory will be placed in the same category as universities canceling classes and sending students home, or airports and tourist attractions emptying — all of them examples of a flight to safety, the surrender of grand plans and big ambitions in favor of a desire to just survive.
… [T]here was no way — even with Biden’s age and verbal stumbles — for a consummate outsider like the Vermont senator to portray himself as the most plausible choice to deal with such a mortal threat
Ross Douthat, Joe Biden Beat Bernie Sanders. But So Did the Pandemic