  We study the spin-charge separation in a Kondo-like model for an impurity
with a spin and a charge (isospin) degree of freedom coupled to a single
conduction channel (the ``spin-charge'' Kondo model). We show that the spin and
charge Kondo effects can occur simultaneously at any coupling strength. In the
continuum (wide-band or weak coupling) limit, the Kondo screening in each
sector is independent, while at finite bandwidth and strong coupling the
lattice effects lead to a renormalization of the effective Kondo exchange
constants; nevertheless, universal spin and charge Kondo effects still occur.
We find similar behavior in the two-impurity Anderson model with positive and
negative electron-electron interaction and in the two-impurity
Anderson-Holstein model with a single phonon mode. We comment on the
applicability of such models to describe the conductance of deformable
molecules with a local magnetic moment.
