Palin should have been given a national platform and exposure in 2008; brought to the Senate for greater breadth of experience, then run as part of a ticket in 2012.
What some pundits ignore is that you don't need a polarizing figure who only attracts your base - to win, youi need to appeal to the central, undecided voter. News flash: despite popular mythology, the US is a largerly urban society. Sarah's appeal was primarily to core rural Republican voters - who weren't going to vote Democrat under any conditions.
Urban voters saw a small town, white trash family with a knocked-up teenage daughter and her redneck high-school drop-out boyfriend. Not inspirational.