Biden reiterated that he asked Obama not to endorse him, and he stuck by that stance even when asked whether he’d want Obama’s backing if the field narrowed to three people.

“No, because everyone knows I’m close with him,” Biden said. “I don’t need an Obama endorsement.”

Biden went on to say that as Obama’s vice presidential pick, he provided crucial relationships with the base of the Democratic Party, including with African Americans, and with voters in places such as Pennsylvania, Colorado, Virginia and Florida..

“I was the one who was sent in,” he said. “And the reason was, because all the polling and data showed that I had those relationships with the base of the Democratic Party as well as African-Americans. And so I did as many African Americans events as Barack did.”

Biden was asked about a POLITICO Magazine article that recently reported how Obama had confided in another candidate that his former vice president “really doesn’t have it” when it comes to an intimate connection with voters.

“He may have said that. And if it’s true, and he said it, there’s truth to it,” Biden acknowledged on Monday before saying that he has “mostly campaigned for other people in the time I’ve been here. And I’ve never been in a position seeking the nomination where I have had the money and the organization to be able to get open headquarters all over the state.”

On his prospects in Iowa and beyond, Biden said that if he won the first caucus state, it would be “awful hard to stop me from winning the nomination.”

Biden lamented media coverage that he said initially dismissed the durability of his candidacy because he was too moderate and didn‘t embrace policies like Medicare for All. Biden said the field was now moving closer to his views and away from the left. When asked whether he unintentionally set the stage for Buttigieg, who is leading in the polls in Iowa, Biden grew animated.

“Set it up? He stole it! Set it up?” Biden said of the mayor of South Bend, Ind.

When asked whether Buttigieg now had the enthusiasm and the moderate positioning, he again scoffed. “No, he doesn’t have the enthusiasm and the moderate — moderate plan. It’s the Biden plan.”

The former vice president then accused the media of going too easy on Buttigieg, saying his opponent had once supported a more liberal health care plan but then pivoted. Buttigieg embraces a plan he calls “Medicare for All Who Want It,“ and he has advertised heavily in Iowa and other early-voting states on that proposal.

Biden contended that if he had supported one plan then shifted toward another plan that looked like that of an opponent‘s, the media would have shown him no mercy.

"What would you have done to me? You would have torn my ears off," Biden told reporters. "I would be a plagiarizing, no good, old man who did bum bum bum.”

When asked about another polling leader in Iowa and elsewhere — Warren — Biden dismissed her rise and the notion that she had momentum behind her.

“Look at the polling everywhere. Tell me. Tell me where the polling has manifested itself,” he said. “She lives in Massachusetts, she’s invested millions and millions of dollars in New Hampshire, why shouldn’t she be known there?”

Warren’s campaign responded on Monday night.

“Our campaign is not on air in New Hampshire, and we didn't run any TV ads during her 2018 re-election,” said Chris Hayden, a Warren campaign spokesman.

Biden has grown defensive over the level of enthusiasm behind his candidacy and the turnout at his events, which have generally drawn smaller, older crowds in Iowa. While Biden‘s campaign has said the former vice president is running a different campaign with more intimate meet-and-greets, it‘s happening in the face of a recent swell of support for Buttigieg, who has drawn more than 2,000 people at a time in some parts of Iowa.

Biden demanded that reporters give him examples of big crowds for Warren. When a reporter cited a recent large turnout for Warren in Chicago, Biden grew sarcastic.

“Oh, great, she had a showing in Chicago,” he said. “By the way, that’s a wonderful thing. Show me any numbers.”

After the interview, Biden left the bus and boarded a flight to a private fundraiser in Chicago.

Marc Caputo contributed to this report.