McCain picks Sarah Palin

The VP can become president without being elected

Except that VPs are elected alongside their president. If a person doesn't like the idea of a certain person falling into the position of Commander in Chief by their position as VP, then that person can show their opinion by voting for another person for president. But that aside, a presidential candidate is not going to pick someone who has drastically different stances on the issues. In reality, a VP taking position as president would run things in basically the same way regardless. It's not like McCain will get elected, die, then Palin will go apepumpernickel and do things McCain never would. If Palin finds herself filling McCain's theoretical shoes, her actions as president would not vary much (if at all) from what McCain's own actions would be. And the same can be said with "Obama" and "Biden" in place of "McCain" and "Palin" respectively.

And you really can't get mad at McCain for playing the politics game by picking a woman. Obama did the very same thing by picking a person with more "experience".