This is an exellent op ed by David Brooks - it is worth reading because it summarizes why so many people are uncomfortable with McCain having selected Palin as his VP.
http://www.nytimes.com/2008/09/02/opinion/02brooks.html?hp
John McCain is not a normal conservative. He has instincts, but few abstract convictions about the proper size of government. He?s a traditionalist, but is not energized by the social conservative agenda. As Rush Limbaugh understands, but the Democrats apparently do not, a McCain administration would not be like a Bush administration.
The main axis in McCain?s worldview is not left-right. It?s public service versus narrow self-interest. Throughout his career, he has been drawn to those crusades that enabled him to launch frontal attacks on the concentrated powers of selfishness ? whether it was the big money donors who exploited the loose campaign finance system, the earmark specialists in Congress like Alaska?s Don Young and Ted Stevens, the corrupt Pentagon contractors or Jack Abramoff.