A political interest group is a set of individuals organized to promote a shared political concern. Most interest groups owe their existence to factors other than politics. They form for economic reasons, such as the pursuit of profit, and maintain themselves by making profits (in the case of corporations) or by providing their members with private goods such as jobs and wages. Such interest groups include corporations, trade associations, labor unions, farm organizations and professional associations. Collectively, economic groups are by far the largest set of organized interests. The group system tends to favor interests that are already economically and socially advantaged.
Citizens' groups do not have the same organizational advantages as economic groups. They depend on voluntary contributions from potential members who may lack interest and resources, or who recognize that they will get the collective good from a group's activity even if they do not participate (the free-rider problem). These citizens' groups include public interest, single-issue, and ideological groups. Their numbers have increased dramatically since the 1960s despite their organizational problems.
Organized interests seek influence largely by lobbying public officials and contributing to election campaigns. Using an "inside strategy," lobbyists develop direct contacts with legislators, government bureaucrats and members of the judiciary in order to persuade them to accept their group's perspective on policy. Groups also use an "outside strategy," seeking to mobilize public support for their goals. This strategy relies in part on grassroots lobbying--encouraging group members and the public to communicate their policy views to officials. "Outside" lobbying also includes efforts to elect officeholders who will support group aims. Through political action committees (PACs), organized groups now provide nearly a third of all contributions received by congressional candidates.
The policies that emerge from the group system bring benefits to many interests, and in some instances these benefits also serve the general interest. But when groups can essentially dictate policies, the common good is not served. The majority's interest is subordinated to group (minority) interests.