In Kennedy's case, those actors would be senators, not heads of other, potentially belligerent, nations. If appointed, she would be a single vote among 100 and otherwise a placeholder until 2010, when she would have to run for election as any other.
Palin, who one could argue was similarly anointed -- cynically selected without proper vetting -- was headed for much bigger business. As vice president, she would have been a heartbeat away from The Button, though she would not have been "in charge of the U.S. Senate," as she told a child who asked what the vice president does.
Critics on the other side of the political aisle may have had other reasons to oppose Palin (such as her pro-life position), but the loyal opposition was firmly based on substantive concerns about competence, as well as wariness about her tone and temperament, which became increasingly divisive.
Palin's demonstrated lack of basic knowledge, her intellectual incuriosity, her inability to articulate ideas or even simple thoughts all combined to create an impression of not-quite-there.
Few doubt that Palin is here to stay. She is the GOP's chosen closer, as demonstrated in Georgia when she roused the crowds to help re-elect Sen. Saxby Chambliss. What she possesses by immeasurable orders of magnitude -- personal power, presence, pizazz -- one can't purchase. The rest -- theoretically -- she can learn.
Kennedy, a relatively erudite person who has authored several books, may have the political clout to get herself a Senate seat, but it isn't clear that she has the people power needed to sustain her. The electorate eventually will sort out the differences that matter.
In the meantime, a Sen. Caroline Kennedy would not be a nuclear-enabled leader of the free world, whereas a Vice President Sarah Palin might have been.
As such, they are as apples to ... zebras. Their treatment has been commensurate with that difference.