LOL! I seem to remember the exact same thing being said about Ronald Reagan long about March of 1980. We all know how THAT turned out.
That's one example. Barry Goldwater is another. We all know how THAT turned out.
Not saying that Palin is Reagan or Goldwater. Every case has to be weighed on it's merits. Making historical analogies is useful to know how things have worked out before, but past performance of Person A or B 40 years ago doesn't necessarily have direct bearing on Person C in 2011.