  We present a model that incorporates the effect of two-body currents in
quasielastic electron-nucleus scattering within the framework of a consistent
superscaling formalism. This is achieved by defining an averaged single-nucleon
hadronic tensor based on the 1p1h matrix element of the one-body current plus
meson-exchange currents (MEC). The consistent treatment of one- and two-body
currents in our model enables the calculation of exchange current effects in
the kinematical region where the Fermi gas response is zero, but not the
scaling function. The effect of MEC is consistently taken into account when
extracting the phenomenological scaling function from electron scattering data.
With this model, we investigate the effect of MEC on the response functions
taking into account the effective mass of the nucleon, and examine the
consequences it has on the inclusive $(e,e')$ cross section. We find that 1p1h
MEC deplete the quasielastic transverse response, while they not alter
significantly the scaling behavior of (e,e') data.
