This is p. 165
A more plausible explanation lies in the greater number and variety of parties within European countries compared with the United States. Because the Democrats and Republicans have duopolized U.S. politics for more than a century, American scholars have focused on the powerful, studying the only two parties with major impact on national politics. When third parties cast darker shadows on the two-party landscape, scholars have been encouraged to think more generally about parties and have devised typologies to accommodate the interlopers (Rosenstone, Behr, and Lazarus 1984). Otherwise, relatively few U.S. political scientists have been challenged by our party system to build party theory. Crotty's fifty page review of the American literature devoted only four pages to "The Search for Theory" and mostly dealt with the single book by Downs (1957) and various publications by Schlesinger--which have been recently collected in a single volume (1991).
The very nature of the two major U.S. parties has also constrained the development of party theory due to the problem of defining the boundaries of a party to serve as a unit of analysis. In Europe, there is a better-developed sense of formal party membership, sometimes reflected in membership fees, that helps define who belongs to a party. Although most states record party registration for purposes of conducting primary elections, the concept of party members clearly has no national applicability, and the term, "dues-paying member," sounds foreign to our ears. American scholars have attempted to deal with this boundary problem by distinguishing among the "party in the organization" and "party in the government" as opposed to "party in the electorate." But this piecemeal attempt to resolve the problem has not proven to be theoretically fruitful (Schlesinger 1991, 3).
As Pomper noted, "American parties are a jumble of these three conventional forms, which cannot readily be separated" (1992, 146). Pomper's solution was to conceptualize parties in terms of their goals (collective or coalitional), mode of operation (instrumental or expressive), and breadth of focus (elite or mass). These three dimensions produced an eight-fold classification of party concepts. Accordingly, the U.S. Democrats and Republicans are predominantly coalitional and instrumental, with a mass focus--which means they fit Pomper's concept of party as an "office-seeking rational team." Although his conceptualization produced seven other types of parties, the range of concepts is still not broad enough to encompass some parties in cross-national analysis. The issue hinges on choosing a narrow or a broad definition of a political party.
A Narrow definition of "party"
Schlesinger noted that some scholars "want to define party to include all the numerous political organization that call themselves by the name" (1991, 6). He continued, "However useful a theory of party based on such a broad definition would be, the theory I propose to elaborate is less ambitious" and applies only to "parties that contest in free elections, and primarily those parties that are able to win elections over time" (p. 6). Accordingly, Schlesinger adopted the well-known definition by Downs: a party is "a team of men seeking to control the governing apparatus by gaining office in a duly constituted election" (1957, 25). Many scholars employ a comparably narrow definition, perhaps excluding entities that they would commonly regard as a party in other countries.
This contradiction was apparent in Neumann's Modern Political Parties (1956), one of the first collections of studies in comparative politics. In his concluding essay, Neumann wrote, "Only the coexistence of at least one other competitive group makes a political party real," and said, "A one-party system is a contradiction in terms" (p.395). Nevertheless, Neumann's reader included an article on the Communist Party of the Soviet Union. Despite the way he defined a party, even Neumann found it awkward not to regard communist parties as political parties (see also Epstein 1975, 233). To do otherwise would exclude a huge body of literature important to comparative politics (Fischer-Galati 1979, Szajkowski 1986, Timmerman 1987, Gilberg 1989, Narkiewicz 1990). Moreover, Randall (1984, 4) contended that this "Eurocentric" definition would exclude non-communist one-party systems in third world countries, and, as Pempel pointed out in his book on one-party dominant regimes, "The vast majority of the nation-states in the world could be characterized as one-party states" (1990,1).
Focusing on parties' functions in contesting elections tends to exclude the class of "anti-system" parties, which Sartori defined as ones that undermine the legitimacy of the regime (1976, 132-133). For example, communist parties in multiparty systems often participated only tactically in elections (Gilberg 1989 and Narkiewicz 1990). A definition based in electoral competition would also exclude militant religious, ethnic, and regional, parties that operate on the fringes of the political system. For instance, McDonald and Ruhl noted that only "a few" of the more than 125 active parties in Latin America play the roles "attributed to them in the general theoretical literature--literature that is based on Western European and Anglo-American systems in which military obedience and legislative power are taken for granted" (1989, 3).