Under capitalism, political power tends to become concentrated in the executive branch of government, along with a corresponding decline in the effectiveness of parliamentary institutions. As Paul Sweezy points out, parliaments grew out of the struggle of capitalists against the power of centralised monarchies during the early modern period, and hence the function of parliaments has always been to check and control the exercise of executive power. For this reason, "parliaments flourished and reached the peak of their prestige in the period of competitive capitalism when the functions of the state, particularly in the economic sphere, were reduced to a minimum." [Theory of Capitalist Development, p. 310]

As capitalism develops, however, the ruling class must seek to expand its capital through foreign investments, which leads to imperialism, which in turn leads to a tightening of class lines and increasingly severe social conflict, as we have seen earlier (see section D.5.2). As this happens, legislatures become battlegrounds of contending parties, divided by divergent class and group interests, which reduces their capacity for positive action. And at the same time, the ruling class increasingly needs a strong centralised state that can protect its interests in foreign countries as well as solve difficult and complex economic problems. "Under the circumstances, parliament is forced to give up one after another of its cherished prerogatives and to see built up under its very eyes the kind of centralised and uncontrolled authority against which, in its youth, it had fought so hard and so well." [Ibid., p. 319]

This process can be seen clearly in the history of the United States. Since World War II, power has become centralised in the hands of the president to such an extent that scholars now refer to an "imperial presidency," following Arthur Schlesinger's 1973 book of that title.

Contemporary US presidents' appropriation of congressional authority, especially in matters relating to national security, has paralleled the rise of the United States as the world's strongest and most imperialistic military power. In the increasingly dangerous and interdependent world of the 20th century, the perceived need for a leader who can act quickly and decisively, without possibly disastrous obstruction by Congress, has provided an impetus for ever greater concentration of power in the White House.

This concentration has taken place in both foreign and domestic policy, but it has been catalysed above all by a series of foreign policy decisions in which modern US presidents have seized the most vital of all government powers, the power to make war. And as they have continued to commit troops to war without congressional authorisation or public debate, their unilateral policy-making has spilled over into domestic affairs as well.

In the atmosphere of omnipresent crisis that developed in the fifties, the United States appointed itself guardian of the "free world" against the Red Menace. This placed unprecedented military resources under the control of the President. At the same time, the Eisenhower Administration established a system of pacts and treaties with nations all over the globe, making it difficult for Congress to limit the President's deployment of troops according to the requirements of treaty obligations and national security, both of which were left to presidential judgement. The CIA, a secretive agency accountable to Congress only after the fact, was made the primary instrument of US intervention in the internal affairs of other nations for national security reasons.

With President Johnson's massive deployment of troops to Vietnam, the scope of presidential war-making power took a giant leap forward. Unlike Truman's earlier decision to commit troops in Korea without prior congressional approval, the UN had not issued any resolutions to legitimate US involvement in Vietnam. In justifying the President's decision, the State Department implied that in the interdependent world of the twentieth century, warfare anywhere on the globe could constitute an attack on the United States which might require immediate response, and hence that the Commander-in-Chief was authorised to take "defensive" war measures without congressional approval or UN authorisation.

Following Vietnam, the presidency was further strengthened by the creation of an all-volunteer military, which is less subject to rebellions in the face of popular opposition to a foreign war than a conscripted force. With their control over the armed forces more secure, presidents since Nixon have been liberated for a much wider range of foreign adventures. The collapse of the Soviet military threat now makes it easier than ever for the President to pursue military options in striving to achieve foreign policy objectives, as the Persian Gulf conflict clearly showed. United States involvement there would have been much more difficult during the Cold War, with the Soviet Union supporting Iraq.

It is sometimes argued that Watergate fatally weakened the power of the US presidency, but this is not actually the case. Michael Lind lists several reasons why [in "The Case for Congressional Power: the Out-of-Control Presidency," The New Republic, Aug. 14, 1995]. First, the President can still wage war at will, without consulting Congress. Second, thanks to precedents set by Bush and Clinton, important economic treaties (like GATT and NAFTA) can be rammed through Congress as "fast-track" legislation, which limits the time allowed for debate and forbids amendments. Third, thanks to Jimmy Carter, who reformed the Senior Executive Service to give the White House more control over career bureaucrats, and Ronald Reagan, who politicised the upper levels of the executive branch to an unprecedented degree, presidents can now pack government with their spoilsmen and reward partisan bureaucrats. Fourth, thanks to George Bush, presidents now have a powerful new technique to enhance presidential prerogatives and erode the intent of Congress even further — namely, signing laws while announcing that they will not obey them. Fifth, thanks also to Bush, yet another new instrument of arbitrary presidential power has been created: the "tsar," a presidential appointee with vague, sweeping charges that overlap with or supersede the powers of department heads.

As Lind also points out, the White House staff that has ballooned since World War II seems close to becoming an extra-constitutional "fourth branch" of government The creation of presidential "tsars" whose powers overlap or supersede those of department heads is reminiscent of the creation of shadow governments by Hitler and Stalin (see also section D.9.2 - What is "Invisible government"?).

Besides the reasons noted above, another cause of increasing political centralisation under capitalism is that industrialisation forces masses of people into alienated wage slavery, breaking their bonds to other people, to the land, and to tradition, which in turn encourages strong central governments to assume the role of surrogate parent and to provide direction for their citizens in political, intellectual, moral, and even spiritual matters [see Hannah Arendt, The Origins of Totalitarianism, 1968]. And as Marilyn French emphasises [in Beyond Power], the growing concentration of political power in the capitalist state can also be attributed to the form of the corporation, which is a microcosm of the authoritarian state, since it is based on centralised authority, bureaucratic hierarchy, antidemocratic controls, and lack of individual initiative and autonomy. Thus the millions of people who work for large corporations tend automatically to develop the psychological traits needed to survive and "succeed" under authoritarian rule: notably, obedience, conformity, efficiency, subservience, and fear of responsibility. The political system naturally tends to reflect the psychological conditions created at the workplace, where most people spend about half their time.

Reviewing such trends, Ralph Miliband concludes that "[h]owever strident the rhetoric of democracy and popular sovereignty may be, and despite the 'populist' overtones which politics must now incorporate, the trend is toward the ever-greater appropriation of power at the top" [Divided Societies, Oxford, 1989].