The possibility of electron beam formation during breakdown in a gas-filled diode for nitrogen at the atmospheric pressure is analyzed theoretically. The propagation speed of the plasma channel in the gap and its conductance is estimated for different conditions. It is shown that the distortion of the electrical field in the interelectrode gap results in formation of the conditions sufficient for generation of runaway electrons. The calculations have demonstrated that the experimentally obtained current switching rates could be explained only by formation of highly conducting plasma channels at the early stage of the breakdown. The estimates of the switching rates within the plane model of the plasma front give the propagation speeds of the plasma front that are several orders of magnitude lower than those observed experimentally.