A republic isn't defined by hidden power. You're defining a symptom of the problems they often face.
A republic is defined by that which its constituents allow to manifest. If maleficence persists in its efforts where diligence is discouraged by embracing tolerance, then decline is inevitable. If diligence persists over maleficence, then the subversion is rendered helpless by the doctrine of provable Truth. Truth can only be discovered by freedom of speech, press, (belief) religion, and most importantly, petition of the Government for a redress of grievances. A government that doesn't allow for the last is in the beginning stages of a dictatorship.