Because the Government is complicated and fundamentally unaccountable, only special interests can afford to get involved in the political system, since the costs of entry are high, and involvement is not cost-effective for the average Citizen: according to John Gardner (Secretary of Health, Education and Welfare in the Johnson Administration), it is a mistake to think of the Federal Government as a unified entity; rather, "[i]t is a collection of fragments under the virtual control of highly organized special interests . . . In the special-interest state that we have forged, every well-organized interest owns a piece of the rock."
This consequence was known to the Framers, and was properly feared. In fact, Madison was acutely aware of the threat that special interests (called "factions" in 1787) would acquire an undue influence over Government, and even devoted a famous essay, Federalist 10, to an examination of this concern. To Madison, preventing the threat of faction control of Government was a key role for any constitution. Amazingly, however, Madison dismissed the most critical problem society would face in one sentence! As Elliot (1985) reported,
What has not attracted sufficient notice about Madison's argument in Federalist 10, however, is the cavalier way in which he dismisses 'minority Factions' as a potential threat to the public interest:If a faction consists of less than a majority, relief is supplied by the republican principle, which enables the majority to defeat its sinister views by regular vote, it [a minority faction] may clog the administration; it may convulse the society; but it will be unable to execute and mask its violence under the forms of the constitution.Madison's argument that popular elections are sufficient to insure that minority interest groups do not pose a serious threat to the public interest is simply wrong. Madison's argument depends on the assumption that majorities will take the steps necessary to inform and organize themselves to protect their self-interest, but this assumption is demonstrably wrong, as Mancur Olson has shown in his recent book, The Rise and Decline of Nations. 
Madison was wrong because Majority organization is not cost-effective when the benefits of organizing are very slight (i.e., individual Government actions with potential Majority opposition, such as tax loopholes for special interests, result in only a slight cost to individuals who are not a part of the favored Minority) - and the costs of organizing a Majority around discrete issues are high. No such debilitating effects affect the well-organized special interests, who a) have the funds to organize, b) have a cost-effective financial interest to organize [e.g., a tax loophole can have enormous short-term financial consequences for the special interest], and c) are unified on the issue which most affects them. Compounding these effects, as Elliot further observed, the passage of time has eroded whatever natural checks there were against the ability of special interests to capture the Government:
[The Framers] carefully crafted a political system in which various elements of the federal government would be elected by different constituencies in the hope that diversity in the distribution of interests among the varying electoral constituencies would prevent any special interest group from exercising undue influence over the government as a whole. . . .The house of Representatives being to be elected immediately by the people, the Senate by the State legislatures, the President by the electors chosen for that purpose by the people, there would be little probability of a common interest to cement these different branches in a predilection for any particular class of electors.The basic institutional checks designed by the framers of the Constitution to limit the power of interest groups have long since eroded. First, the seventeenth amendment provided direct popular election of Senators. Second, the electoral college has now become largely vestigial, so that as a practical matter, the President is also popularly elected. Third, a vast "administrative state" with broad delegated powers has arisen that lies largely outside the system of checks and balances crafted so carefully by the framers. Finally, as both the country and the nature of government have changed, the principle of geographic diversity of interests, upon which the framers placed primary reliance, is no longer as potent a check on the power of special interest groups as it may once have been. Today there are many interest groups that are more or less evenly distributed throughout the country (social security recipients, for example), and they can bring potent electoral pressures to bear on Representatives, Senators, and Presidents alike.The cumulative effect of these changes is to render our political institutions systematically vulnerable to the influence of well-organized, narrowly-focused groups seeking subsidies or other forms of preferential treatment from the federal government. The current deficit is merely the outward symptom of these more fundamental problems, resulting from the way in which our political institutions have evolved. 
The existence of latent structural flaws became apparent when the Nation began incurring its first serious budget deficits in the late 60's (as a consequence of the Vietnam War). The Government began its slow and inevitable decline, as the special interests began to consolidate their power. By 1978, the systemic nature of our infirmities had become clear, and in November of that year, The New York Times devoted a three-part series to an examination of this breakdown in Government:
John Gardner, the founder of Common Cause, the public-affairs lobby, says the nation is being whipsawed by a multiplicity of special interest groups, resulting in 'a paralysis in national policymaking.'
Daniel Bell, professor of sociology at Harvard, said at a recent meeting of the American Jewish Congress: 'Our political institutions do not match the scales of economic and social reality. The national state has become too small for the big problems of life and too big for the small problems.' . . .Tom Hayden says 'You can take any issue you want, and the system isn't delivering. There is no glue holding the country together.'
From the White House, Stuart Eizenstat, President Carter's chief adviser for domestic affairs, speaks of 'an increasingly fragmented society.'
Disarray in government and dissatisfaction with it have always been part of the American system. John F. Kennedy is remembered, for example, as a forceful, charismatic President but one who was unable to effect relatively mild reforms in the early 1960's after having run on a promise to 'get this country moving again.' . . .
[T]here is a consensus that no coalition of interests is strong enough to set priorities for the overall public good to effect reforms that have wide public support, to root out inefficiency and corruption in government programs, and to inspire confidence in political leadership.
Many see this disunity as systemic, and therefore separate from, the failures of individual leaders and institutions, the complex new issues that have arisen in recent years and the voter frustration and discontent stemming from government failures.
'I'm not sure anybody could pull this Government together,' Representative Morris K. Udall, Democrat of Arizona, remarked . . . .
Congress has decentralized itself until every special interest has access to policy, but the leadership cannot put broad policy objectives into effect.
More and more members of Congress see themselves and present themselves as ombudsmen for their states or districts, rather than as representatives trying to effect broad national and foreign policies. . . . 
In a telling prediction, Fred Wertheimer, the senior vice president of Common Cause, noted that:
'It is a Congress becoming more and more paralyzed in its ability to make decisions on behalf of all citizens. It is a Congress that in the not-too-distant future will be drowning in special-interest group political money.'