The reversible properties of cluster phases have been described by theories that invoke Coulomb interactions as a stabilizing mechanism. What is lacking so far is direct measurement of these charges. This contribution aims at predicting what to expect if electrophoresis measurements were to be performed on these systems. As a result, we get a picture that exhibits several interesting features: (1) The existence of monomers and clusters lead to distinctly different mobilities (zeta potentials) in a single sample. (2) Strong dependence of the mobilities on particle volume fraction. It is our aim that the theory outlined in this paper may serve as a guideline to interpret the expectedly "messy" electrophoretic measurements.