There are a number of approaches toward explaining who has power in a community or some other political unit. Among these: elitism, pluralism, participatory democracy, representative democracy, technocracy, and so on. The basic text on pluralism? Robert Dahl's case study of New Haven, CT, published first in 1961.
His argument was that, in this city, decision making power was divided among different groups. One set of groups was involved in, for instance, urban development. Another set in education policy within the city. Still another set of groups with respect to political nominations and elections. No single elite dominated across these issues. Hence, in his judgment, power was divided.
Elected officials, too, had a role to play. The city's mayor, Richard Lee, was at the head of an "executive-centered coalition."
The central importance of this case study is its elaboration of pluralism, the politics of competing centers of power, in action. As such, it remains a classic in the world of political science.