Radical polymers, a class of polymers with robust radical pendent groups along their backbones, have demonstrated various applications as next generation energy storage materials. Among all the aliphatic radical polymers, poly(2,2,6,6-tetramethylpiperidinyloxy methacrylate) (PTMA), a poly(methacrylate) bearing the persistent 2,2,6,6- tetramethylpiperidinyloxyl (TEMPO) radical as a pendent group, has received increasing interest since its first introduction to a rechargeable battery. As the insulating nature of PTMA is straightforward and has been well-recognized among electrochemists, it is surprising that conductivity of ~ 10^-6 S/cm was observed in neat PTMA films in 2013. The mechanism of this efficient electron transport was proposed to be charge hopping when the spacing between two adjacent radicals is less than 10 Å. In this study, we find that PTMA is highly insulating –conductivity in the range 10^-11 S/cm – regardless of the synthetic method of preparation. We have compared these results with variable range hopping theory and find that very few radical sites are electrically active, though the stable radical sites are closely packed. On the other hand, regioregular polythiophene backbone has also been incorporated into the stable radical polymer structure and radical pendent group content was varied systematically. Using EPR and electrical conductivity measurements, we show that there is an exponential decrease of conductivity as we increase the percentage of pendent groups attached to repeating units, which changes the conductivity by 6 orders of magnitude between the non-radical control polythiophene material and the material with highest radical content (~80%). The conductivity of the solid films can be further improved by doping with oxidizers. These findings serve as an important guide to the future design of radical polymers on conjugated backbones with the goal of increasing conductivity for redox-active energy storage applications.