  The \textit{I-V} characteristics of four conducting polymer systems like
doped polypyrrole (PPy), poly 3,4 ethylene dioxythiophene (PEDOT),
polydiacetylene (PDA) and polyaniline (PA) in as many physical forms have been
investigated at different temperatures, quenched disorder and magnetic fields.
Transport data clearly confirm the existence of a \textit{single} electric
field scale in any system. Based upon this observation, a phenomenological
scaling analysis is applied, leading to extraction of a concrete number $x_M$,
called nonlinearity exponent. The latter serves to characterize a set of
\textit{I-V} curves. The onset field $F_o$ at which conductivity starts
deviating from its Ohmic value $\sigma_0$ scales as $F_o \sim \sigma_0^{x_M}$.
Field-dependent data are shown to be described by Glatzman-Matveev multi-step
tunneling model [JETP 67, 1276 (1988)] in a near-perfect manner over nine
orders of magnitude in conductivity and five order of magnitudes in electric
field. $x_M$ is found to possess both positive and negative values lying
between -1/2 and 3/4. There is no theory at present for the exponent. Some
issues concerning applicability of the Glatzman-Matveev model are discussed.
