A perturbation analysis of diffusion-reaction systems exposes the effect of local thermal equilibrium as an extremal property of systems which minimize dissipation. The effect is also shown to be sufficient for stability of small perturbations relaxing towards steady-states close to equilibrium. Several variational principles are constructed for perturbations in chemically reacting systems with simultaneous transfer of heat, mass and electric charge. The underlying physical principle, which substantiates the joint role of thermodynamic potentials and intensity of dissipation, is invariance of the energy dissipation. The formulations of perturbed dynamics include : a nonstationary extension of Onsager’s principle, gradient representations with a perturbed vector of thermal displacement, perturbed potentials of thermal field, and functional Hamiltonian formalism. Each formalism works with the assumption of local thermal equilibrium which, in our analyses, isa common property of asymptotic states of various orders. An important result is inclusion of chemical reactions into perturbational dynamics, with chemical nonlinearities governed by the standard kinetics of mass action law. We also present a novel method, based on equivalent variational problems. which implies transformations between various thermodynamic potentials at nonequilibrium.