Pluralism in a democracy is the widespread distribution of political power and influence within the state and civil society. Individuals and groups can express different points of view freely, independently, and effectively in order to influence public opinion and the decisions of government.

One indicator of pluralism in a democracy is a variety of interest groups, which put forward in the public domain competing points of view about public issues and policies. An interest group is an independent, nongovernmental organization that puts pressure on government officials to make decisions that collectively favor the members of the group. Sometimes an interest group is called a pressure group, because of the intensity of its effort to influence government decisions.

Unlike a political party, an interest group neither nominates candidates for election to public office nor tries to win control of the government through the electoral process. However, interest groups do participate in election campaigns by supporting individual candidates and political parties that favor their point of view. Interest group members also use the mass media and face-to-face interactions with people to influence public opinion in favor of their positions on public issues.

Interest groups are formed in a democracy in order to represent and advance the competing interests of different segments of the society and economy. For example, in the United States, there are many interest groups that promote the viewpoints of particular industries, such as the producers or sellers of petroleum, firearms, timber, dairy products, and coal. Labor unions are interest groups that represent workers in various occupations. Still other interest groups address particular topical concerns such as environmental protection, conservation of natural resources, needs of consumers, and the rights of women.

Pluralism in a democracy is exhibited by the existence of multiple competing centers of power. Various nongovernmental organizations, including interest groups, compete to promote their particular goals and their different visions of the common good. These private organizations are subject to the rule of law under a constitution, but they are beyond the direct control of government officials.

By contrast, the robust pluralism of a constitutional democracy is weak or absent in non-democratic systems. In a totalitarian regime, such as the defunct Soviet Union, pluralism is not permitted. It is against the law to form free and independent nongovernmental organizations. Civic and political participation is encouraged, but only on the restrictive terms of the ruling party, which controls all social organizations and political groups in its regime.

Pluralism is also diminished under the authoritarian regimes in countries such as the Kingdom of Saudi Arabia and the Republic of Iran. Political and social groups, especially religious groups outside the Islamic mainstreams of these societies, are either outlawed, suppressed, or otherwise marginalized. – John Patrick, Understanding Democracy, A Hip Pocket Guide