From Commentary's Contentions Blog:
Palin will be a failed pick if her conduct between now and November 4 reveals that she does not have the judgment to be a heartbeat away; that her comportment is not what we would wish of our leaders; and that she does not seem large enough for the office. A great many things will go into determining all of those things, as they are right now with Barack Obama — and, incidentally, John McCain, who has every qualification for the presidency one could imagine except that he hasn’t won an election for it yet.
The effort to pre-determine her unfitness is not only a losing proposition; there is something fundamentally foolish, about it. Even un-American, in the sense that it suggests rule by wonk rather than popular fiat. Ask Bill Clinton, who tried his best to make the case against Barack Obama and then stood on stage on Wednesday night explaining to America that people were saying about Barack Obama just what they had said about him, Bill Clinton, 16 years ago. That is what interesting elections do. They up-end expectations.