The positive aspect of the influence or role of special interest groups in democratic political systems is the opportunity such groups or organizations provide in influencing governmental policies when those groups' perspectives might otherwise not be heard. In a country as geographically expansive and heavily populated as the United States, and as diverse in terms of ethnicities, political orientations, professions, cultures, and so on, the ability of any one individual to make a difference at the national or even state or local level would be very limited. The seat of the federal government, of course, is in Washington, D.C., on the eastern coast of the United States. Individuals or groups in, say, Oregon, Alaska, Hawaii, or even locations much closer to the nation's capital would have a very difficult time being heard in the halls of Congress or in the Executive Branch if they did not unite and form what are pejoratively called "special interest groups." In fact, so central is the right of the public to "lobby" the institutions of government that it is set forth in the First Amendment to the Constitution of the United States:

"Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the government for a redress of grievances." [Emphasis added]

To the extent that special interest groups exist to petition the government, then their existence and operation is entirely consistent with the intent of the Founding Fathers of the United States. Special interest groups provide organized groups of people a voice with their government, and that voice is constitutionally protected.

The negative aspect of special interest groups is the undue influence small categories of people can wield with the government. Powerful special interest groups may only represent the perspectives of a very small percentage of the population, but enjoy influence with the government out of all proportion to that percentage. Other groups may be larger, but still enjoy more influence than their numbers may warrant. While protection of the minority is an essential component of a liberal democracy, caution should be used in ensuring that the preferences of that minority are not allowed to dictate public policy at the expense of the majority. Equal protections under the law means just that: equality. It does not mean government by the few over the many. 

The most negative aspect of special interest groups involves the extremes to which some such groups go in advancing their interests. Under occasional circumstances, the relationships between special interest groups and elected representatives can grow way too close, with the latter becoming beholden to the former because of the often-nefarious influence of political donations proffered by organized groups. The relationship of money to elective politics remains highly divisive in the United States, and U.S. Supreme Court rulings affirming the right of groups to contribute financially to political candidates, while perhaps valid on strict legal merits, has done nothing to help protect the interests of the less prosperous. It is within this context that special interest groups can have a very deleterious influence on democratic processes.

An additional advantage to the interest group is that it provides strength in numbers in a way that is different from the geographical strength in numbers that our system of elected representatives is based upon.  People who band together to promote their special interest may be widely scattered, with too few people in a congressional district, for example, to have any influence through the electoral process.  A fairly non-controversial example of this would be people interested in genealogy, who lobby the government to promote the availability of records that are valuable to them, such as birth certificates and death certificates.  It is wildly unlikely that this would be an issue in a campaign or that there would be enough genealogists in a particular district or state to sway a campaign. Yet, for this group, this is an important matter it wishes to weigh in on.  Another example would be AARP, which represents the interests of senior citizens. In a given state or congressional district, there is usually not a majority of senior citizens that could be a dispositive factor in an election.  So, senior citizens from all over the country join together and have the power of their numbers to try to influence policy and law in a way that benefits them.  Without the ability to gather sufficient numbers geographically, people on their own are not likely to have much influence at all.

The major positive aspect of interest groups is that they give the people better ways to influence their representatives on a day to day basis.  One fundamental aspect of democracy is that the people should control the government.  However, it is difficult to do so when all we do is vote every 2 years, 4 years, or 6 years depending on the office.  Interest groups fill this gap.  Interest groups lobby members of government every day.  This makes government officials aware of the people’s opinions and desires every day instead of just at election time.  This makes our system more democratic.

The major negative is that interest groups can give money too much of a role in politics.  Interest groups work best when they have a lot of money.  They use it to hire good lobbyists and to give campaign contributions, among other things.  If money becomes very important, then only the people and groups that have a lot of money will have their voices heard.  This can reduce the quality of democracy by favoring the voices of the rich over those who have less money.