I really believe that the McVain campaign didn’t have a clue as to who they were getting when McVain picked Sarah Palin. They were expecting a”be seen but not heard” church mouse kind of woman who would fade into the background so Johnny-boy could shine. They grossly underestimated Sarah’s intelligence, her common sense and her down-home populist appeal that drew conservatives to her in droves. It was not long before conservatives like me were saying, “drop McVain and put Sarah at the top of the ticket”, as the McVain crowd went ballistic. They need to face up to the fact that McVain lost the election for the Republican ticket, not Sarah.
Matthew Continetti has more on this in his book. Palin was fully vetted by A.B. Culvahouse. McCain, Mark Salter and Schmidt knew everything.
However, in their zeal to "one-up" the press on the VP pick, they kept the choice and all the background info secret from everyone else on the campaign staff. Nobody else knew anything about her and when the press started their feeding frenzy, the campaign was helpless to respond.
A screw-up from the get-go.