  Gas-liquid criticality in the ultrasoft restricted primitive model (URPM) of
polyelectrolytes is studied using the collective variables-based theory. For
the model, an effective Hamiltonian is derived and explicit expressions for all
the coefficients are found in a one-loop approximation. Based on this
Hamiltonian, the phase and critical behaviour is analysed. Our results provide
evidence that the nature of the gas-liquid criticality in the URPM is the same
as in the restricted primitive model that includes a hard core.
