Schumer told Mitchell flat out that he, other leading Dems, and the Dem party were all solidly behind Lieberman in the primary and that he wouldn't go beyond that right now. Mitchell, not expecting such a strong statement of support from Schumer, tried to make something of the fact that he didn't say anything about who they would support after the primary, as if somehow they would pull their support from him, if he won the primary! As if that made any sense at all! She suggested that Schumer was waffling, even said, "sounds like what the meaning of 'is' is...." In fact, and as much as I dislike Schumer, he made a very clear straight forward reply, but it didn't fit with Mitchell's pre-prepared response and she wound up looking like she was trying to pound a square peg into a round hole.
Schumer was right and Mitchell made a fool out of herself by pressing a question that was obviously not going to be changed from his original answer.
Having said that, my understanding is Schumer, other Democrats and the radical base are actively working against Joe Lieberman. Schumer has to be supportive in public but the others don't.