  We investigate the dynamical and steady-state spin response of the
nonequilibrium Anderson model to magnetic fields, bias voltage, and temperature
using a numerically exact method combining a bold-line quantum Monte Carlo
technique with the memory function formalism. We obtain converged results in a
range of previously inaccessible regimes, in particular the crossover to the
Kondo domain. We provide detailed predictions for novel nonequilibrium
phenomena, including non-monotonic temperature dependence of observables at
high bias voltage and oscillatory quench dynamics at high magnetic fields.
