Addressing worries about the Biden team's war chest, campaign manager Greg Schultz on Monday tweeted that the campaign had raised more money in October and November than it did in all of the last quarter. Still, Biden has lagged Buttigieg, Bernie Sanders and Warren in fundraising; the latter two especially have built out much larger online grassroots operations than Biden.

“Biden’s been in the race since April, and despite ups and downs, and many gaffes and missteps, and attacks by many of the other candidates, he’s still standing as the overall frontrunner,” said Garry South, a Democratic political consultant from California who long expressed doubts about his home state senator’s presidential bid. “So there’s something to crow about, I would say.”

At least some of Biden’s self-assuredness is about "Medicare for All." Biden noted in an interview Monday on his campaign bus that Democrats doubted his candidacy early on because he would not embrace a complete remake of the health care system. Now, he said, other candidates are paying a price in the polls for embracing Medicare for All and are moving toward his plan.

Biden quickly objected when he was asked to lay out his path in Iowa given his enthusiasm gap with other candidates, including Warren.

“You don’t see that [enthusiasm] with Warren. Stop kidding a kidder, OK? Come on, man. Give me a break,” Biden said. At first Biden said the enthusiasm for Warren was lacking in Iowa but then he added: “And everywhere, look at the polling everywhere. Tell me — tell me where this great enthusiasm has manifested itself?”

Biden partly walked back those remarks after an event in Mason City on Tuesday.

“I think there is enthusiasm for her,” Biden said. “The point I was making was that I don’t think the bulk of the enthusiasm in the Democratic Party is for Medicare for All. There is enthusiasm for people who support that. … I don’t think that is where the center of the party is or the left or the right of the party is."

Another looming threat for Biden is Bloomberg, a billionaire who in a matter of weeks dumped nearly $60 million on television.

When asked on Monday how he felt about Bloomberg’s candidacy, and the possibility that he would spend hundreds of millions of dollars of his own money, Biden essentially shrugged it off.

“Look at the other billionaire, what has he spent, 35 million bucks? OK, well, show me what it’s done,” Biden said, referring to Tom Steyer, who just qualified for the December Democratic debate. “You can’t sit and say if someone’s going to spend $200-$300 — up to a billion of their own money — you can’t say, 'Don’t worry about that at all.' But … we’ll see. I don’t discount it, but I don’t spend any time thinking about it. Nothing I can do about that. Zero.”

Biden’s confidence also rests on his position in South Carolina and a raft of Southern Super Tuesday states that include more diverse populations and more conservative Democrats. To that end, Biden said Monday, if he faltered in Iowa, he could still win the nomination. But if he won Iowa, Biden argued he’d be almost unstoppable.

And Biden said he doesn’t see anyone even close to him in South Carolina polling who could surge even if they won Iowa.

“There is no one else who is in a position to all of a sudden to do what Barack [Obama] was able to do," he said. "I think even if we didn’t do well in Iowa, we’re still way in the game in terms of where we are on Super Tuesday and where we’ll be in South Carolina and Nevada. I feel confident about those two, and I don’t see something fundamentally shifting."

"The reason why it’s so important in Iowa — if the reverse happened, if I were to come in here and win this … and then do well in New Hampshire. Then what stops it?”

Even a now-former Harris campaign aide said Biden was more resilient than her team predicted.

“Look, Biden is a lot tougher than all of us gave credit for,” the aide said. “And the fact is that the polls don’t lie. He’s got solid support from the [African American] community. Now is he unbeatable? No. But I don’t see Cory [Booker] or Deval [Patrick] making it or significantly cutting into his support with African Americans.”

