Tensions appeared to remain high immediately after the conclusion of the debate, when Warren (D-Mass.) and Sanders (I-Vt.) were caught on video holding a brief yet animated discussion after Warren declined to shake Sanders's hand.
The once cordial relationship between Sanders and Warren has turned contentious in recent days. During the debate, Warren and Sanders provided conflicting accounts of a private conversation they had in 2018 about gender and politics.
Warren said Sanders disagreed with her view that a woman could win the presidential election. Sanders contends that he merely outlined what he said would be Trump's efforts to defeat another female candidate, and in the debate, he said, "Of course a woman can win."
The video of the post-debate exchange shows Sanders extending his hand as Warren approaches him onstage. Rather than shaking it, Warren clasps her hands together and speaks to Sanders. He responds, as Tom Steyer walks toward them. Both Warren and Sanders have serious expressions on their faces.
Warren and Sanders then separate. Steyer and Sanders shake hands on one side of the stage. Nearby, Warren shakes hands with former South Bend, Ind., mayor Pete Buttigieg.
It's unclear from video of the exchange what Sanders and Warren said to each other. Representatives for the Warren campaign declined to comment.
After the debate, Steyer told MSNBC’s Chris Matthews that he did not know what Warren and Sanders said to each other.
“All I was trying to say was to both Senator Warren and Senator Sanders was it’s great to see you, thank you for participating in this. And whatever they were going on with each other, I was trying to get out of the way as fast as possible,” said Steyer, a billionaire environmentalist.