The two candidates, who are competing for the most progressive voters in the Democratic Party, had seen their apparent nonaggression pact fray in recent days — seemingly culminating in Warren spurning Sanders' gesture on national television. She shook former Vice President Joe Biden's hand just moments before.
The rift between the senators was accelerated by a story, first reported by CNN, that Sanders had told Warren in late 2018 he did not think a woman could win a presidential election.
"Well, as a matter of fact, I didn't say it," Sanders said Tuesday evening in response to a question from the CNN moderators asking him why he had made that statement to his fellow senator. "Anybody who knows me knows that it's incomprehensible that I would think that a woman could not be president of the United States."
That answer did not appear to satisfy Warren, however, who responded, "I disagreed," when CNN moderators asked her what she thought, "when Senator Sanders told you a woman could not win the election."
Warren went on to point out that she and Sen. Amy Klobuchar, D-Mass., had won every single election they had ever run in, a feat none of the men onstage could claim.
'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 have been in are the women — Amy [Klobuchar] and me.'
"Can a woman beat Donald Trump?" Warren asked. "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 have been in are the women — Amy [Klobuchar] and me.
"And the only person on this stage who has beaten an incumbent Republican any time in the past 30 years is me," she continued, referencing her 2012 victory over former Sen. Scott Brown, R-Mass.
Tuesday's debate was the final chance voters will get to see all the top candidates on the same stage before the first-in-the-nation Iowa caucuses, which can make or break presidential primary campaigns.