  We review a three-dimensional formalism that provides a systematic way to
include relativistic effects including relativistic kinematics, the effects of
negative-energy states, and the boosts of the two-body system in calculations
of two-body bound-states. We then explain how to construct a conserved current
within this relativistic three-dimensional approach. This general theoretical
framework is specifically applied to electron-deuteron scattering both in
impulse approximation and when the $\rho \pi \gamma$ meson-exchange current is
included. The experimentally-measured quantities $A$, $B$, and $T_{20}$ are
calculated over the kinematic range that is probed in Jefferson Lab
experiments. The role of both negative-energy states and meson retardation
appears to be small in the region of interest.
