One of the most devastating indictments of the manner in which political "science" courses are taught in our colleges and universities today is the muck of contradictions that passes for the notion of a "political spectrum."
A "spectrum," according to Webster's, is defined as "a continuous range or entire extent." Observe that this definition does not designate the identity of the phenomenon, but only the manner in which it makes its nature manifest: a varying characteristic that forms a sequence of intermediate values between two opposing extremes.
Without those two opposing extremes the concept of a "spectrum" collapses into insensibility: one would never speak, for instance, of a rainbow with two red edges, or of a thermometer with a boiling point at each end.