VP potentials-how do they know when they've been bounced?

Factual Questions
1

I was just watching the news and they said that Mitt Romney is out. How does Mitt know he’s out? Assuming he, or any candidate, doesn’t remove himself from the running, how do they know that they didn’t get the nod?

Thanks,
greatshakes

2

I’m sure someone from the presidential campaign tells them. If you’re on the short list, it’s probably the candidate himself.

You want to treat the people you contact very nicely. One story had it that one reason why Eugene McCarthy challenged Johnson in 1968 because Johnson had leaked McCarthy’s name as being a potential VP in 1964, even though he had no intention of choosing him.