The article presents a critical discussion of the model of polarized pluralism formulated by Sartori (1976), and in particular of the hypothesis that a high number of political parties, together with a marked polarization of the uni-dimensional political space, will produce centrifugal drives in the party competition. Through a formal analysis, it will be argued that in a polarized or ideologized space of competition the centrifugal drives do not prevail, because even the anti-system parties are ultimately forced to some centripetal shifts. The interaction of the strategies employed by pro and anti-system parties are illustrated in a typology. Secondly, searching for a proxy indicator of the centripetal tactics employed by the anti-system parties, a revision of Sartori’s index of coalition potential is further introduced. Anchoring on standards of the coalition theory, the paper puts forward a conceptual schema that allows the identification of four types of parties, with high or low coalition potential, complementary parties, and blackmailing parties