Poly(o-toluidine) emeraldine base (EB) has been protonated with D,L-camphor sulfonic acid (HCSA). The CSA-doped poly(o-toluidine) (POT-CSA) is completely soluble in m-cresol, and the electrical conductivity is similar to 28 S/cm. The incorporation of CSA has been proved by means of UV-Vis and IR spectroscopy. Thermogravimetric (TG)/mass (MS) analysis shows that POT-CSA is stable up to 180 degrees C indicating the processability with other insulating polymers upto this temperature. TG curve of POT-CSA yields a four step decomposition pattern, and the degradation of the polymer backbone starts at 430 degrees C. The thermal elimination of CSA occurs in the temperature range of 180 to 430 degrees C. The viscometric and spectroscopic results suggest the change in molecular conformation from the compact coil to the expanded coil type which is enhanced by increasing the protonation level of EB by the addition of HCSA. The conductivity data were well equivalent to the viscometric data. Furthermore, POT-CSA-ABS (acrylonitrile/butadiene/styrene) blends were successfully fabricated with an extremely low percolation threshold of 2.66%. The scanning tunneling microscopic (STM) results reveal that the low percolation threshold reflects the formation of interconnecting path of conducting particles in ABS matrix.