  We employ an effective Lagrangian approach to derive the leading-logarithm
two-loop electroweak contributions to the muon anomalous magnetic moment, a_mu.
We show that these corrections can be obtained using known results on the
anomalous dimensions of composite operators. We confirm the result of Czarnecki
et al. for the bosonic part and present the complete sin^2 \theta_W dependence
of the fermionic contribution. The approach is then used to compute the
leading-logarithm three-loop electroweak contribution to a_mu. Finally we
derive, in a fairly model-independent way, the QED improvement of new-physics
contributions to a_mu and to the electric dipole moment (EDM) of the electron.
We find that the QED corrections reduce the effect of new physics at the
electroweak scale by 6% (for a_mu) and by 11% (for the electron EDM).
