Inequality of groups:
Those on the right of the political spectrum argue that at the very least, pressure groups operate within a series of 'competing elites'.
They argue that because each group represents the interests of it's clients, it is entirely compatible with a democratic society.
However, those on the left argue that this 'competition' is often one that is unequal.
C.Wright Mills continued this theme in his 1956 book 'The Power Elite'; asserting that the oligarchy maintained social and economic dominance through their vast financial and human resources.
For example: the resources of trade associations such as theNational Association of Realtors, outweigh those of enviromental protectionist groups.
However, cases such as 'Brown v. Board of Education Topeka' (1954) illustrates that groups such as the NAACP can be successful in achieving their aims, and that the oligarchy have not completely monopolised influence.