A running tool sets and pressure tests a bridging hanger and a packoff in a single trip. The running tool has a stem, an inner body, and a piston. The inner body is connected to the stem so that rotation of the stem relative to the inner body will cause the stem to move longitudinally. The piston is connected to the stem so that the stem and piston rotate and move longitudinally in unison. A piston engagement element is housed in the inner body and is adapted to engage the piston when the bridging hanger is set to prevent premature setting of the packoff. The piston engagement element can be disengaged once the bridging hanger is set, thereby allowing the piston to set the packoff.