  In this article we study in detail the prospects of determining the infrared
finite QCD effective charge from a special kinematic limit of the vertex
function corresponding to three background gluons. This particular Green's
function satisfies a QED-like Ward identity, relating it to the gluon
propagator, with no reference to the ghost sector. Consequently, its
longitudinal form factors may be expressed entirely in terms of the
corresponding gluon wave function, whose inverse is proportional to the
effective charge. After reviewing certain important theoretical properties, we
consider a typical lattice quantity involving this vertex, and derive its exact
dependence on the various form factors, for arbitrary momenta. We then focus on
the particular momentum configuration that eliminates any dependence on the
(unknown) transverse form factors, projecting out only the desired quantity. A
preliminary numerical analysis indicates that the effective charge is
relatively insensitive to the numerical uncertainties that may afflict future
simulations of the aforementioned lattice quantity. The numerical difficulties
associated with a parallel determination of the dynamical gluon mass are
briefly discussed.
