The phenomenon of nuclear lightning is reexamined with theoretical models and laboratory-scale experiments. It is shown that the distribution of electric space charge, rather than the electric field alone, must be considered in accounting for the shapes and locations of nuclear lightning channels in the atmosphere. A self-consistent distribution of space charge requires a consideration of both electronic and ionic conduction in the irradiated atmosphere, in agreement with earlier findings (Grover, 1980). The magnitudes of nuclear lightning currents (105--106 A) (Colvin et. al, 1987) are compatible with predictions for electrical conduction currents based on contemporary theory. Comparisons between the theoretical predictions and laboratory discharge experiments for the nuclear lightning case emphasize the dominant influence of electric space charge on discharge paths in solid insulators and thunderclouds. ¿ American Geophysical Union 1988