In a conductor at equilibrium, the electric potential remains constant due to the absence of electric fields within the conductor, which prevents the movement of charge carriers like electrons. If the potential were not constant, electrons would experience a force causing them to move, disrupting the equilibrium. The concept of equilibrium in this context refers to a state where the electric potential is uniform throughout the conductor. This uniformity ensures that there are no net forces acting on the electrons, maintaining stability. Therefore, the electric potential must be constant in a conductor at equilibrium to prevent charge movement and maintain a balanced state.