In this work, we investigate the origin of PCM's SCF convergence effects and identify applicable molecular systems. We have found that the PCM-induced SCF convergence improvement is most prominent in molecules with charge separations, such as zwitterions. We will analyze the formalism of the conductor-like PCM (CPCM) and show its preference for converging to a polarized solute and the selective stabilization of molecular orbitals (MOs) based on the local electrostatic environment. Then we will use a set of small zwitterionic molecules and zwitterionic peptides to show the effects of CPCM in reducing density-driven DE and improving SCF convergence, which is superior to the traditional SCF convergence technique, level shifting. We will show that two effects of PCM lead to improved SCF convergence: (1) an increased HOMO-LUMO gap that reduces the mixing of occupied and virtual orbitals, and (2) the stabilization/destabilization of selective MOs is consistent through all SCF iterations.