Can a presidential candidate change their mind on their running mate or is that decision set in stone?

Question

Once a presidential candidate chooses a running mate, is he stuck with that choice or can he change his mind and select a different running mate? If so, has this ever happened before?

Answer 1

Never happened, unlikely now!

Answer 2

Palin actually has to be nominated at the convention. If she was incredibly unpopular for some reason McCain could be forced to accept another name on the ticket. Palin has pretty good support from the conservative base so this won't happen, but it remains a possibility.

Answer 3

You can change your mind all the way up to being voted into office, once after that takes place an impeachment process would be required to remove a sitting VP.

Answer 4

I doubt it. For how long we waited to get Biden and Palin, they better not change it.