  We develop a Lorenz- and gauge-invariant dynamical model for pion
electroproduction in the resonance region. The model is based on solving of the
Salpeter (instantaneous) equation for the pion-nucleon interaction with a
hadron-exchange potential. We find that the one-particle-exchange kernel of the
Salpeter equation for pion electroproduction develops an unphysical singularity
for a finite value of $Q^{2}$. We analyse two methods of dealing with this
problem. Results of our model are compared with recent single-polarization data
for pion electroproduction.
