Having been born in Alaska, very near Wasilla, with numerous relatives still living there, I can tell you that there are many Minnisotans dwelling in those parts. The accent is certainly a blend of Northern Tier speak. Personally, I find it quite endearing and very American!
As opposed to east coast aberative English.
Hey, I have a typical southeastern Pennsylvania/south New Jersey/northern Delaware accent, and despite the large amounts of liberals in my home region, our accent is PLENTY American, thank you very much. Let’s not start generalizing political view by accent. The best counter-examples of this are Bill Clinton, John Edwards, and Jimmy Carter.
While Palin's accent does have a Minnesota sound overall, I have noticed that she does not have the characteristic long o's.