Complex sentence: Hartman said that a phased approach would give horsemen and owners sufficient time to adjust to the change, and thinks that the regulators are the only voice in North American racing for the horse.
Split into simpler sentences: Hartman said that a phased approach would give horsemen and owners sufficient time to adjust to the change. Hartman went on to say that he thinks that the regulators are the only voice in North American racing for the horse.