The notion that winning the White House would be a downward trend in the career of an individual is completely absurd.
I’m sure it’s privately considered absurd even by those in the anti-Palin movement (they have publicly pretended otherwise ever since they first invented the absurdity a few months ago).
Losing the Republican primary would be a serious downer in her career. Losing as Mitt Romney’s running mate, for example, would be even worse.