McCain doesn't get it
Why would he do this, one reason because of his ignorant condescending belief that choosing a female that he will get the Hillary voters. Women should be outraged.
The first and most important quality in choosing a Vice President is are they qualified to be Commander in Chief, clearly McCain has not done that.
This is once again another in a litany of examples of the fact that John McCain is clueless.
Obama chooses an accomplished leader like Joe Biden and McCain picks the former runner up to Miss Alaska. What a difference.
***update** The McCain campaign per NBC news has said they picked Palin not because she was ready to step in as Commander in Chief if necessary but that she will get more media coverage.