  The target normal single-spin asymmetry in inclusive electron-nucleon
scattering is studied in the low-energy regime that includes the $\Delta$
resonance. The particular interest in the asymmetry resides in that it is
driven by two-photon exchange effects. It probes the spin-dependent absorptive
part of the two-photon exchange amplitude, which is free of infrared and
collinear singularities and represents the most pristine expression of
two-photon exchange dynamics. The study presented here uses the 1/Nc expansion
of QCD, which combines the $N$ and $\Delta$ through the emergent SU(4)
spin-flavor symmetry in the baryon sector and allows for a systematic
construction of the transition EM currents. The analysis includes the first
subleading corrections in the 1/Nc expansion and presents results for elastic
and inelastic final states. The asymmetry is found to be in the range
$10^{-3}-10^{-2}$. The $\Delta$ resonance plays an important role as an
intermediate state in the elastic asymmetry and as a final state in the
inclusive asymmetry.
