A purely magnetospheric model is introduced for observed abrupt changes in pulsar radio profile. Motion of magnetospheric plasma is described by a drift frequency, ω dr , that depends on a parameter 0 ≤ y ≤ 1, and a change in the magnetospheric state corresponds to a change in y . Emission is assumed to arise from m spots distributed uniformly around the magnetic axis, so that spots drift by at the rate mω dr . Observable features, such as subpulses, appear to rotate as ω R = ω dr − mω V . The motion of the visible point, ω V , is ignored in a “standard” version of the viewing geometry that assumes a fixed line of sight (rather than a fixed line-of-sight direction), implying ω V = 0. With ω V ≠ 0, the apparent motion of subpulses is not constant. An abrupt (or more gradual) change in y implies a change in ω R , which affects the observed pulse structure and the average profile. We apply the model for profile shifts observed with PSR B0919+06.