  Pulsars often display systematic variations in the position and/or intensity
of the subpulses, the components that comprise each single pulse. Although the
drift of these subpulses was observed in the early years of pulsar research,
and their potential for understanding the elusive emission mechanism was
quickly recognised, there is still no consensus on the cause of the drift. We
explore the electrodynamics of two recently proposed or refined drift models:
one where plasma lags behind corotation, connecting the drift with the
rotational pole; and another where plasma drifts around the electric potential
extremum of the polar cap. Generally, these are different locations, resulting
in different drift behaviours, that can be tested with observations. In this
study, however, we specifically examine these models in the axisymmetric case,
where the physics is well understood. This approach seems counter-intuitive as
both models then predict similar large-scale plasma drift. However, it allows
us to show, by studying conditions \emph{within} the sparks for both models,
that the lagging behind corotation (LBC) model is inconsistent with Faraday's
law. The modified carousel (MC) model, where plasma drifts around the electric
potential extremum, not only aligns with Faraday's law, but also provides a
future direction for developing a comprehensive model of plasma generation in
the polar cap region. Unlike previous models, which considered the drift only
inside the discharging regions, the MC model reveals that the electric field
\emph{between} the discharges is not completely screened, and plasma drifts
there -- a paradigm shift for the drifting subpulse phenomenon.
