In Caesar's Women, Colleen McCullough has Caesar intimate that Cicero coined the term Populares, but did he? That question arose during tonight's book chat. Though the word seems almost a fixation of Cicero's, the answer is no and can be found at JSTOR:
Cicero and the Word Popvlaris [Cicero and the Word Popularis]
The Classical Quarterly, New Series, Vol. 22, No. 2 (Nov., 1972), pp. 328-338
Published by: Cambridge University Press on behalf of The Classical Association
Stable URL: http://www.jstor.org/stable/638213
It has by now become a commonplace among the historians of the republic that optimates and populares were not political parties in any modern sense. Nevertheless the ghost of the 'popular party' still lingers in subtle disguises, the most insidious of which is donned whenever populares is translated as 'the populares', with all that the definite article may imply. It is the aim of this paper to catalogue the principal functions and connotations of the word popularis in Cicero, with illustrative material from other sources, in the hope that such a demonstration may contribute to the final laying of the ghost. The first section is essentially a commentary on the definition of populares given in the Pro Sestio; the second attempts to expound the various techniques that Cicero uses to combat an opponent who claims to be popularis.
Later on, the author writes:
It would probably be wrong to suppose that Cicero's treatment of populares displayed any great originality. Despite the inadequacy of our sources, precedents for most of his arguments can be found. The notion of the sovereignty of the whole people had been brilliantly exploited by L. Crassus in 106, when with an audacity equal to Cicero's in 63 he presented the judiciary law of Q. Caepio as a popularis measure.
It's a fascinating article and well worth reading for those who have access to JSTOR or old volumes of The Classical Quarterly.
Hat tip N.S. Gill