Easy. He made a large enough contribution to the GOP to get on the mailing list for this fundraiser.
Ah well money talks. But surely there is some background checks made before someone is invited. Surely not everyone can get in the door by making a monetary contribution.
"Surely not everyone can get in the door by making a monetary contribution."
Apparently they can. Some heads may roll (behind the scenes, of course) over this goof. I hope security is better at the actual event.