It was a trick question. Laura Bush was probably caught off guard by it. Her response was fairly innocuous, "I think that's possible," but it leaves the door open for the left to bash conservatives as sexists, quoting the President's wife as their authority, and then for the right to get angry at Laura Bush for saying such a thing.
It's true that the White House and press secretary have been extremely stupid with their charges that ALL their critics are elitists and sexists and extremists and what not. Far from it. Most of the critics are respected members of the conservative movement, with the few obvious exceptions that can be discounted.
Various accounts have said that Laura Bush played an important part in convincing her husband that Miers would be a fine nominee, which exacerbates the case. Still, Bush is responsible for making this stupid decision, not Laura.
Uh, she said a lot more than, "I think that's possible".
She also said:
I do PR/media training for a living. Laura Bush was without a doubt prepped for her Today Show appearance with multiple on-camera mock interview sessions. This question (and an on-message answer to it) would have been practiced numerous times -- it would hardly be unexpected.
Depending on the White House message/goal for this interview, her answers could have ranged from what she said, to "I think in most cases it's more likely that her critics are simply unaware of x, y, z about the candidate..." to "No, I believe the vast majority of her critics are sincere, but wrong -- and here's why..." The fact that she didn't even follow the "It's possible, I think it's possible" with a "BUT" is telling.
While it's possible that she merely flubbed/forgot her media training, the fact that her answer was a soft echo of Gillespie's statement at least implies that the "critics are sexist" message may be a White House talking point meant to triangulate (i.e., sell out the base). The fact that the rest of her statement was a litany of statements designed to be similarly appealing to undecideds/moderate liberals supports the hypothesis that this was a deliberate message point.