I couldn't say it any better than this.

Which is why I'm hijacking this post.

Nate of FiveThirtyEight: (my bold)

On the other hand, when a vice president takes over for a president, the nation is necessarily undergoing a crisis, because the death (or resignation) of a president is perhaps as traumatic an event as can reasonably be imagined (in the "best" case resulting from a slowly-developing illness, and the worst, an attack by terrorists or foreign adversaries).

From Lincoln though Clinton, Americans have frequently been willing to gamble on a relatively inexperienced President, exchanging some assurances of near-term readiness for longer-term upside (what might be described as "vision"). But the optimal skill set for a vice president is somewhat different. "Vision" hardly matters; a vice president taking over for a president will not get to name his own cabinet, and will initially at least be left to execute upon somebody else's agenda. Instead, the readiness component is rendered more important.

I suspect most Americans grasp this on a gut level, even if they aren't quite able to articulate it. Which is why, to my gut instinct, I think Americans can feel sympathy for Sarah Palin, can believe she's the sort of person they'd want to have a beer with -- and still find her a detriment to McCain's case for the White House.

Exactly.