According to the pluralist theory, the source of influence lies in a group's ogranizational structure, their resources, human resource and connections they have.
In effect, the pluralist theory suggests that the source of influence lies in the modern Lobbying groups.
Today, there are numerous lobbying groups in Washington that try to influence government policy, laws, legislations etc.
The effectiveness of these lobbying groups actually lies in how well they can manage all of their resources for maximum results.