In this paper, we present the theoretical results of a self-consistent kinetic simulation, clarifying the influence of runaway electron flows on a delay time of the switching stage of a nanosecond discharge. The simulation is based on an accurate numerical solution of the Boltzmann kinetic equation, with model collision integrals that take into account elastic and ionization collisions of the electrons with neutral atoms. As an example, the breakdown of a cylindrical gap is investigated with respect to the variations of the voltage rise time value. The current and voltage time profiles, power spectrum, and current of high-energy electrons, as well as the electron distribution function, are calculated accordingly. Our numerical solution agrees with the existent experimental data.