That is up to McCain. All of duties are pre-decided when

VP is being nominated. The same goes to Biden. For guy like Biden to accept VP, he has to tell Obama what he would like to do as VP. When an agreement is reached, the nomination open to public

As far as Palin, she can do a lot of things. VP role is very flexible position. You can become very powerful guy like Cheney or you can play traditional role like attending ceramonies or being special representative for President on some special missions. You can facilitate neigociation with congress. The choices are a lot

Key question on Palin is whether or not she can step in in case of something bad happened to McCain.

I, for one, think she can