A downhole tool having a first packing element and a second packing element configured to synchronically set to selectively hydraulically isolate a portion of the wellbore. The lower packing element may be first set against the well with the upper packing element next being set against the well. A slip joint permits a change in distance between the packing elements during the setting of the packing elements. The slip joint may be energized to apply a force to the lower packing element to prevent the unsetting of the lower packing element during the setting of the upper packing element. A resilient member may be used to energize the slip joint or the slip joint could be hydraulically or pneumatically energized. Once both packing elements are set, the wellbore may then be treated by flowing fluid out of a ported sub positioned between the packing elements.