I went to see Sarah Palin in Richmond, VA last fall. 30,000 plus people standing in the heat for HOURS to see and hear her speak. Meanwhile, McCain was doing good to get 5,000 people show up to hear him campaign.
Unfortunately, I believe Sarah Palin was trashed beyond repair by the media making her unlikely to be an effective candidate in 2012, but without her on the ticket in 2008 I doubt if McCain would have received 35% of the vote.
Also, no matter who conservatives pick, the left will Bork and Palinize. If we dump Palin and turn to someone new in 2011, they will have a fresh attack ready, that will still be fresh in 2012.