Remember that there may be two or three special interest groups with different positions on the same subject. Take gun control legislation. The NRA and other organizations are against it, then there are organizations that fight for any control they can get. Both are constantly trying to influence congress to pass laws in their favor. Each side represents the feelings of thousands or millions of members. Unions are a special interest group, and so is AARP. In some cases, congress has better access to information by listening to these different groups than if they had to investigate everything on their own. The problem arises when some group is very small and has the money to influence legislation. Take the Trial Lawyers Association...probably not anywhere near as many people belong to it as belong to AARP, but they have a lot of financial influence.