How powerful is the American President?

Is he the world's most powerful man?

On the face of it, yes. As chief executive of the world's only superpower, he is boss of 2.7 million employees (2 per cent of the US labour force) and commander-in-chief of the mightiest army on earth. At all times he is accompanied by the so-called 'football', a briefcase containing America's nuclear launch codes. He can negotiate treaties, pardon criminals and appoint around 4,000 senior officials (though many require the Senate's consent) including ambassadors, judges, generals and cabinet ministers.

Whence does he derive his powers?

In contrast to the ill-defined powers of the British PM, his are defined in a document: Article II of the US Constitution (signed in 1787). Yet the powers thus assigned don't sound that impressive. Scarred by memories of war with King George III, most of the 56 Founding Fathers wanted to create a weak central leader (a "foetus of monarchy"), to let Congress make the laws, and to keep most power in the hands of state and local legislatures. But they were also in thrall to the trustworthy figure of George Washington, the revolutionary general widely expected to be the first man to hold the new office. That helps explain the ambiguous nature of some of his defined powers (eg. the duty "to take care that laws be faithfully executed"), an ambiguity that over time the president has systematically exploited.

And how did the presidency develop in the early years?

Washington, elected in 1789, was conscious of his role in shaping the office ("If I may use the expression, I walk on untrodden ground"). Sensitive to public fears of an over-mighty executive, he enshrined many self-limiting customs - an egalitarian term of address ('Mr President'), cabinet meetings and term limits that only later became law. His minimal activism, and that of the next five presidents, reassured the public. Only when the seventh president - Andrew Jackson, a firm believer in a strong presidency - took on both Congress and the Supreme Court in the 1830s, were the constraints on presidential power put to serious test.

What are those constraints?

The structure of American government, it's often said, is "an invitation to struggle": power is divided between executive and legislature, while authority to interpret the Constitution rests with the Supreme Court. The president's cabinet, unlike the British PM's, cannot contain sitting members of the legislature; and Potus can never be sure of a legislative majority. The Founding Fathers wanted Congress to initiate policy, and for a century after Andrew Jackson, it largely did so, the president playing a mainly oppositional role. Only after the New Deal of Franklin Roosevelt (1933-45) did the kind of presidential programme now being prepared by Obama and McCain become institutionalised.

Is he now America's lawmaker?

He has certainly become the largest source of new legislation. And though he may not vote in Congress, if he doesn't like a bill he can veto it. His veto can only be overridden by a two-thirds majority in the Senate, which has only happened 107 times (4 per cent of attempts) in the history of the US. But then again, he too