What sort of claim? If the dolly+car caused damage to another vehicle or property, your motorhome liability pays. If the car falls of the dolly and gets damaged, the car 's own collision or comprehensive policy pays.
In a nutshell, the motorhome policy pays for any damages it causes (liability) and any damage to the motorhome itself (collision & comprehensive).
You really don't have to sort that out yourself. If the towed vehicle gets damaged, just file a claim with the towed vehicle insurer and include info on how it happened. They will deal with the other insurer if they feel some other policy should pay (called subrogation).
Former owner of 2004 American Tradition and several other RVs
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC