What was bizarre about it was how half-assed she was about it. Iirc the story was basically a week or two of being based on nothing more than “someone who works/worked for Warren said that Sanders said X”, then Warren basically just said “Sanders said something about X, but I’m not discussing it. End of story.”

So she didn’t really seem to go on the attack (to capitalise on it and try do some actual damage to his reputation), but neither did she defuse it (perhaps by saying something about it being out of context and that she didn’t believe him to be sexist), and she didn’t deny what her staffer claimed (her comment confirmed that she believed it to be accurate).

It just made her look bad, and harmed her chances with people who were on the fence between the two of them because he’s probably the candidate with the most overlap with her in voters.