Strategically, it might make sense to invite all the candidates to participate in this. The one who issues the invitation ….. 1. Is demonstrating that he has nothing to fear from the other candidates, 2. Is demonstrating that since it was he who issued the invitation, he is the leader by definition. 3. Puts the other candidates in a bit of a quandary and awkward position since it would hurt them if they refuse to join the rally and 4. Is showing that while they all want to be the nominee and need to beat up on each other to get there, a display of a united front to the party is important particularly on this issue since after all, it’s really the other party that they need to beat.
All those candidates? Can they handle a crowd that size??