Interest groups are organizations that represent shared policy goals and try to influence the policy process. They pursue their goals through lobbying, gaining access to decision makers, litigation, and going public to mobilize support. There are many theories that explain interest group influence, including pluralism, which argues groups compete democratically, and elite theory, which claims a powerful upper class rules. Successful interest groups are small to avoid free rider problems, focus on intense issues, and have financial resources to access politicians. They use propaganda techniques like plain folks, transfer, and bandwagon appeals to shape public opinion.