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.
Barry Goldwater never reached the popularity level of Ronald Reagan. Reagan was able to get the conservative Democrats and the Independents to vote for him. I believe that if Sarah had the microphone, as a candidate, she’d be able to get her positive message out, and folks tired of Obama might just cotton to it.