Perhaps the most intriguing moment of Tuesday’s Democratic debate came moments after it had concluded.
Senator Bernie Sanders, fresh off two hours of verbal sparring with other candidates that included a clash with Senator Elizabeth Warren over whether he told her in a private 2018 meeting that a woman could not be elected president, reached out to offer her a handshake.
But Ms. Warren did not reciprocate.
The pair then briefly exchanged words; Mr. Sanders gesticulated at Ms. Warren, turned and walked away.
The moment, captured on video as the candidates mingled after the debate in Iowa, punctuated a high-stakes night for Mr. Sanders and Ms. Warren, two of the leading contenders for the Democratic nomination for president. After days of increasing tensions between their campaigns, they confronted each other directly over a dispute that has upended their longtime truce and disheartened left-wing voters weeks before the Iowa caucuses.
Pressed by debate moderators, Mr. Sanders strongly denied that he had made such a comment in the December 2018 meeting.
“I didn’t say it,” Mr. Sanders said of the remark, which emerged in a news report on Monday and Ms. Warren later confirmed. “Anybody knows me knows that it’s incomprehensible that I would think that a woman cannot be president of the United States.”
Ms. Warren held firm, saying as she had in a statement on Monday that she “disagreed” with Mr. Sanders’s assessment about who could win.
“Bernie is my friend, and I am not here to try to fight with Bernie,” she said. “But look, this question about whether or not a woman can be president has been raised and it’s time for us to attack it head-on.”
What she and Mr. Sanders said in their post-debate exchange remained unclear early Wednesday.
One possible witness, the former hedge fund executive Tom Steyer — who is seen in the video standing nearby — told reporters he had been unable to hear what was said.
And asked for her thoughts on the interaction between her Senate colleagues, Senator Amy Klobuchar of Minnesota said simply: “I get along with everyone onstage.”
The existence of the 2018 meeting between Ms. Warren and Mr. Sanders has been public since shortly after it happened. The New York Times previously reported that Ms. Warren had sought it “as a courtesy,” and that neither senator had tried to gain the other’s support or discourage the other from running. Ms. Warren and Mr. Sanders were the only people in the room.
But new details about the meeting were first reported by CNN on Monday. Other outlets, including The Times, confirmed the CNN report. Mr. Sanders went on to accuse the Warren campaign of “lying” about the episode before Ms. Warren issued her statement Monday night, which said in part: “Among the topics that came up was what would happen if Democrats nominated a female candidate. I thought a woman could win; he disagreed.”
At the debate on Tuesday night, Mr. Sanders said that voters could find video online of him “talking about how a woman could become president” and added that he had “deferred” to Ms. Warren in 2015 when he said there “was a movement” to draft her as a presidential candidate.
“Let me be very clear,” he said. “If any of the women on this stage or any of the men on this stage win the nomination — I hope that’s not the case, I hope it’s me — but if they do, I will do everything in my power to make sure that they are elected in order to defeat the most dangerous president in the history of our country.”
For her part, Ms. Warren said she believed “the best way to talk about who can win is by looking at people’s winning record.”
“So, can a woman beat Donald Trump? Look at the men on this stage,” she said. “Collectively, they have lost 10 elections.”
“The only people on this stage who have won every single election that they’ve been in are the women,” she said, offering praise for Ms. Klobuchar. “Amy and me.”
Ms. Warren also said she was the only person on the stage who had beaten an incumbent Republican at any time in the past 30 years, a claim Mr. Sanders later sought to fact-check, noting that he had defeated an incumbent Republican running for Congress.
“When?” Ms. Warren asked, kicking off an odd exchange over math.
“1990,” Mr. Sanders said.
Ms. Warren then appeared to count backward in her head.
“That’s how I won,” Mr. Sanders said. “Beat a Republican congressman.”
“Thirty years ago,” Ms. Warren interjected as Mr. Sanders sought to make another point. “But wasn’t it 30 years ago?”
“I beat an incumbent Republican congressman,” Mr. Sanders reiterated.
“And I said, I was the only one who’s beaten an incumbent Republican in 30 years,” Ms. Warren said, appearing slightly incredulous.
”Well, 30 years ago is 1990, as a matter of fact,” Mr. Sanders said. “But I don’t know that that’s a major issue of the day.”
Ms. Warren and Mr. Sanders have long been friendly — a point Ms. Warren reiterated in her statement on Monday — and both have sought to advance progressive ideas throughout the primary. But their paths to this point have differed.
Mr. Sanders ran an unexpectedly competitive race against Hillary Clinton in 2016 that transformed him into something of a global sensation on the political left. And as time has passed, the Democratic mainstream has embraced elements of his message, such as the need for universal health care. But some political observers doubt Mr. Sanders’s ability to expand his appeal beyond his base in a general election.
Ms. Warren, in the meantime, has presented herself as a scourge of Wall Street — a target she shares with Mr. Sanders. But she has worked aggressively to win over a wider range of supporters and has sought to draw a contrast between herself as a capitalist and her self-identified democratic socialist colleague, Mr. Sanders.
“The real danger that we face as Democrats is picking a candidate who can’t pull our party together or someone who takes for granted big parts of the Democratic constituency,” Ms. Warren said during the debate. “We need a candidate who will excite all parts of the Democratic Party, bring everyone in, and give everyone a Democrat to believe in. That’s my plan, and that is why I’m going to win.”
Here is a transcript of the exchange Ms. Warren and Mr. Sanders had Tuesday:
MODERATOR ABBY PHILLIP: Senator Sanders, CNN reported yesterday, and Senator Sanders — Senator Warren confirmed in a statement — that in 2018, you told her that you did not believe that a woman could win the election. Why did you say that?
BERNIE SANDERS: Well, as a matter of fact, I didn’t say it. And I don’t want to waste a whole lot of time on this, because this is what Donald Trump and maybe some of the media want. Anybody knows me knows that it’s incomprehensible that I would think that a woman cannot be president of the United States. Go to YouTube today. There’s a video of me 30 years ago talking about how a woman could become president of the United States. In 2015, I deferred, in fact, to Senator Warren. There was a movement to draft Senator Warren to run for president. And you know what, I stayed back. Senator Warren decided not to run, and I then did run afterward. Hillary Clinton won the popular vote by three million votes. How could anybody in a million years not believe that a woman could become president of the United States? And let me be very clear: If any of the women on this stage or any of the men on this stage win the nomination — I hope that’s not the case, I hope it’s me — but if they do, I will do everything in my power to make sure that they are elected in order to defeat the most dangerous president in the history of our country.
PHILLIP: So Senator Sanders, I do want to be clear here, you’re saying that you never told Senator Warren that a woman could not win the election?
SANDERS: That is correct.
PHILLIP: Senator Warren, what did you think when Senator Sanders told you a woman could not win the election?
ELIZABETH WARREN: I disagreed. Bernie is my friend, and I am not here to try to fight with Bernie. But look, this question about whether or not a woman can be president has been raised and it’s time for us to attack it head-on. And I think the best way to talk about who can win is by looking at people’s winning record. So, can a woman beat Donald Trump? Look at the men on this stage. Collectively, they have lost 10 elections. The only people on this stage who have won every single election that they’ve been in are the women. Amy and me.
And the only person on this stage who has beaten an incumbent Republican anytime in the past 30 years is me. And here’s what I know. The real danger that we face as Democrats is picking a candidate who can’t pull our party together or someone who takes for granted big parts of the Democratic constituency. We need a candidate who will excite all parts of the Democratic Party, bring everyone in, and give everyone a Democrat to believe in. That’s my plan, and that is why I’m going to win.
PHILLIP: Senator Klobuchar —
AMY KLOBUCHAR: Thank you. Thank you, Elizabeth.
PHILLIP: Senator Klobuchar, what do you say —
KLOBUCHAR: Yes, I would like to —
PHILLIP: Senator Klobuchar, let me finish my question.
KLOBUCHAR: Oh, O.K. I thought it was such an open end — I wasn’t at the meeting, so I can’t comment, but I was going to say —
PHILLIP: What do you say to people who say that a woman can’t win this election?
KLOBUCHAR: I hear that. People have said it. That’s why I’ve addressed it from this stage. I point out that you don’t have to be the tallest person in the room. James Madison was 5-foot-4. You don’t have to be the skinniest person in the room. You don’t have to be the loudest person. You have to be competent. And when you look at the facts, Michigan has a woman governor right now and she beat a Republican, Gretchen Whitmer. Kansas has a woman governor right now and she beat Kris Kobach. And her name is, I’m very proud to know her, and her name is Governor Kelly. Thank you. Third, I would add to this, you have to be a competent to win and you have to know what you’re doing. And when you look at what I have done, I have won every race, every place, every time. I have won in the reddest of districts. I have won in the suburban areas, in the rural areas. I have brought people with me. That is why I have the most endorsements of current Iowa legislators and former Iowa legislators in this race. Because they know I bring people with me. And finally, every single person that I have beaten, my Republican opponents, have gotten out of politics for good. And I think — I think that sounds pretty good, I think that sounds pretty good with the guy we have in the White House right now.
PHILLIP: Senator Sanders, you can respond.
SANDERS: Well, just to set the record straight, I defeated an incumbent Republican running for Congress.
SANDERS: 1990. That’s how I won. Beat a Republican congressman. No. 2, of course —
WARREN: Thirty years ago.
SANDERS: I don’t think there’s any debate up here —
WARREN: But wasn’t it 30 years ago?
SANDERS: I beat an incumbent Republican congressman.
WARREN: And I said, I was the only one who’s beaten an incumbent Republican in 30 years.
SANDERS: Well, 30 years ago is 1990, as a matter of fact. But I don’t know that that’s the major issue of the day.
Reid J. Epstein, Astead W. Herndon, Jonathan Martin and Shane Goldmacher contributed reporting.