Unit 5C: Governing the USA David Houghton The Lecturer in Government at University of Essex writes for BBC Parliament

How rock solid is presidential power?

No other executive position in the world has the status of the US presidency. Both in foreign/military and economic affairs the world looks to the United States for leadership.

And yet the formal powers of the presidency within the American political system are limited; that system was created to frustrate leadership, not to give in free rein, and therein lies the central dilemma of the office.

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What makes a strong president?

The power of the presidency is determined by two sets of rather broad factors: the general historical, institutional and political conditions which prevail at any moment, and the individual leadership characteristics of the president himself.

Under the first category, presidential power is in part a function of factors which are essentially givens; that is, they are to varying degrees beyond the president's control.

The president elected in 2004 will face a domestic and international political landscape which is there whether he likes it or not, and which is only partly amenable to his own efforts to shape or change it.

General historical forces, such as industrialisation, the rise of telecommunications and the decline of political parties have had major impacts on the role and powers of the office.

And yet the president's own personality, beliefs, communicative abilities and management style also help determine the degree to which he is successful.

Different approaches to the presidency tend to emphasise one set of factors over the other, but all are important.

Crises call for a strong leader

Under the first category, presidential power tends to be enhanced when there is a major economic crisis (such as Franklin Roosevelt and the Great Depression) or political crisis (such as Roosevelt and WWII, Lincoln and the Civil War), and is correspondingly reduced when times are ordinary (such as Bill Clinton after the Cold War).

Presidents are also strongest where there is a perception among voters that the president has a mandate to push through major change, usually after the winning candidate in the presidential election has achieved a landslide victory (Lyndon Johnson after 1964).

Where Congress happens to be of the same party or ideology as the president, this can also help to some extent, though party ties are weaker than they are in Britain.

The passage of Ronald Reagan's legislation was helped by the Senate turning Republican from 1981-1986, for example.

On the other hand, under the second category, presidents tend to be strongest where - like Ronald Reagan, John F. Kennedy - they have strong persuasive powers and communicative abilities, as well as legislative skills like Lyndon Johnson's.

When presidents organise the staff around them effectively, this also tends to be associated with effective policy making and the appearance of power.

Has the US presidency become too powerful?

Most contemporary commentators view the presidency as rather weak relative to the expectations it generates.

Unlike the British prime minister, for instance, the American president must work within a system of separated powers.

He is elected separately from members of Congress, and he is not guaranteed their support even when a majority share his party label.

Others analysts, however - notably the historian Arthur Schlesinger - argue that the presidency has become "imperial" in recent years, exceeding the constitutional limits which the Founding Fathers had thought would constrain the office.

Advocates of this position suggest this is especially the case in foreign policy.

For instance, Lyndon Johnson waged the Vietnam War with minimal congressional authorisation and little or no public debate.

On the other hand, some have argued that it is now Congress, not the presidency, which should be described as "imperial".

Supporters of this position allege that Congress now interferes so extensively in the business of the executive that it prevents the latter from functioning effectively and from acting in the interests of the nation as a whole.