As someone who strongly supported Sarah Palin for President, I have come to the conclusion that it will be very difficult for her to defeat Barack Hussein Obama in the 2012 Presidential Election. While I still have a favorable opinion of Sarah Palin, I agree with Chaim that Mike Huckabee would be a better option. Both in terms of electability and in-depth knowledge.
As for what happened in 2008: while some people were turned off by Sarah Palin being on the Republican Presidential Ticket, in my opinion the two factors that lead to BHO " winning" the election were the economy tanking 6 weeks before the election and that McCain ran an ultra politically correct campaign. Especially combined with the vast majority of the media being an extension of the BHO campaign. If Sarah Palin was calling the shots instead of McCain and his key staff members, the results of the election would likely have been significantly closer.