  We compute the leading, chiral charge-changing relaxation term in the quantum
transport equations that govern electroweak baryogenesis using the closed time
path formulation of non-equilibrium quantum field theory. We show that the
relaxation transport coefficients may be resonantly enhanced under appropriate
conditions on electroweak model parameters and that such enhancements can
mitigate the impact of similar enhancements in the CP-violating source terms.
We also develop a power counting in the time and energy scales entering
electroweak baryogenesis and include effects through second order in ratios
$\epsilon$ of the small and large scales. We illustrate the implications of the
resonantly enhanced ${\cal O}(\epsilon^2)$ terms using the Minimal
Supersymmetric Standard Model, focusing on the interplay between the
requirements of baryogenesis and constraints obtained from collider studies,
precision electroweak data, and electric dipole moment searches.
