Peggy Noonan:

What, really, is Mrs. Clinton doing? She is having the worst case of cognitive dissonance in the history of modern politics. She cannot come up with a credible, realistic path to the nomination. She can't trace the line from "this moment's difficulties" to "my triumphant end." But she cannot admit to herself that she can lose. Because Clintons don't lose. She can't figure out how to win, and she can't accept the idea of not winning. She cannot accept that this nobody from nowhere could have beaten her, quietly and silently, every day. (She cannot accept that she still doesn't know how he did it!)