Well it happened before that a Vice President was replaced after the convention. It was not a successful move for the rats. http://www.npr.org/2012/08/04/157670201/the-thomas-eagleton-affair-haunts-candidates-today
However, he was VP, and went peacefully. I think the only way that Hillary is going is either horizontally into an ambulance or dragged from the stage, kicking and screaming, clutching the carpeting.
The possibility of a Biden walk-on has been discussed here for months. I'm wondering if Obama and Jarrett didn't expect an indictment by now, but James Comey has sabotaged their plans by being meticulous.
It's interesting that it's just now beginning to dawn on the liberal media that Hillary might not be a shoo-in.