>>Let’s say we get a brokered convention. Other than John McCain, who would we put on the ticket?<<
While that is a valid discussion to have - its not something I would put a lot of effort into making come about. Brokered conventions had a very short window, about 40 years and were eliminated by the modern primary system.
I think that elimination of the 2/3 requirement for nomination had more to do with it than primaries.