Methods, compositions, kits, and a system are disclosed for detecting one or more analytes in a sample. A mixture comprising the (i) sample, (ii) a first binding reagent comprising a cleavage-inducing moiety and a first binding agent specific for an analyte, and (ii) one or more electrophoretic probes each having a second binding agent is subjected to conditions under which binding of respective binding agents occurs. The interaction between the binding agents and the analyte brings the cleavage-inducing moiety within a proximity effective for cleaving a cleavable linkage tethering an electrophoretic tag to the second binding agent, thereby releasing the tag for electrophoretic separation. Separation of different tags occurs by virtue of their distinct electrophoretic mobilities. After separation, a signal amplification moiety on each tag is activated to generate a signal to indicate the presence of a particular analyte in the sample.