I was honestly surprised to see Biden come in so weak in Iowa and New Hampshire. But maybe I shouldn't have been. As Jonathan Chait points out, in three Presidential runs Biden has never finished higher than fourth in any primary or caucus.
(It is a bit of schadenfreude to see people like Chait -- a pro-war, pro-charter school Democrat who supported Trump's nomination in 2016 on the "he'll be easy to beat" theory -- discomfited by Biden's crash and Sanders's rise.)
Biden has run for president three times. He has not yet managed to finish higher than fourth in any primary or caucus. Biden may, or may not, have been a good enough politician to win a presidential campaign in his prime. He is now well past his prime. His campaigning pace is languid, his debate performances unsettling. And he hasn’t built the kind of campaign apparatus that could drag him over the finish line. He has far fewer endorsements than a traditional Establishment favorite, and his organization has underperformed in Iowa and New Hampshire.