The political process model rejects the idea that the immediate premovement period is the proximate cause of insurgency. Classical and resource mobilization models adhere to a tacit view of insurgency in which social movements are depicted as a direct product of recent or relatively new conditions altering the political environment (McAdam, 1999: 65). For classical theorists, severe structural strain produces impaired functioning in the social system and is portrayed as a proximate cause preceding movement formation (Smelser, 1962; Turner and Killian, 1962). Resource mobilization theorists follow a similar logic in postulating increased resource support for challengers by elites that reduces costs and increases the likelihood of success for contentious action (McCarthy and Zald, 1973, 1977; Oberschall, 1973). Historical forces do not play a prominent role in either of these approaches. In contrast to classical and resource mobilization models, political process theorists look to long-range processes that develop over a protracted period of years prior to movement formation. McAdam's (1982, 1988, 1999) study of black insurgency serves as a template for the political process approach. “Instead of focusing exclusive attention on the period immediately preceding the generation of insurgency,” he states, “the time frame is broadened to include the entire span of years during which conditions facilitative of insurgency are developing. In the case of the black movement, it is the quarter century preceding the 1954 Supreme Court decision in Brown v. Topeka Board of Education that is viewed as especially significant” (McAdam, 1999: 65).