Experiments in inductively driven discharges in the PLT tokamak show an order of magnitude decrease of the electrical resistivity from the Spitzer-Harm value as the density is lowered from 1.5 × 1013 cm−3 to 8 × 1011 cm−3, indicating a corresponding decrease of electron cross-field thermal conductivity as the principal current carriers change from thermal electrons to runaway electrons. The results suggest that electron thermal conductivity in discharges with Spitzer-Harm resistivity may be reduced by increasing the fraction of current carried by runaway electrons with the aid of radiofrequency waves or other means.