Rupert Cornwell: Hail to the chiefs, the real power in the White House

Out of America: Barack Obama may have to jettison his doughty Chief of Staff to get through the present storm

We all know who is the most powerful man in Washington, and by extension the world. But who is the second most powerful? Some note the veneration in which Alan Greenspan was once held, and the crucial role played by his successor Ben Bernanke in saving the United States (and quite probably the entire world) from financial collapse. This school routinely awards the unofficial silver medal to the chairman of the Federal Reserve.

Others would make the case for the man who currently works out of a corner room in the west wing, a couple of doors away from the Oval Office. That man is Rahm Emanuel, the White House Chief of Staff.

There are big differences between the two jobs, not least in security of tenure. Greenspan was chairman for more than 18 years, and outlasted three presidents, while a reconfirmed Bernanke is now into his own second term. Chiefs of staff, by contrast, last an average two and a half years each – and you could say it's a miracle they survive as long as that.

Both men operate primarily in the shadows. But, bouts of market turmoil such as that of 2008 excepted, a Fed chairman's life is relatively sedate; Greenspan is said to have done much of his most productive thinking while enjoying a hot bath. A White House chief of staff however holds half a dozen full-time jobs at once.

As gatekeeper to the Oval Office, he is the man who shapes the president's schedule and determines who the president sees. He is in day-to-day charge of the estimated 2,000-strong staff of the Executive Office of the Presidency. He is also usually a close personal confidant of the president, sometimes even a source of policy ideas. On top of that, he is chief liaison officer of the White House with Congress and the other departments of government.

Throughout history, rulers have relied on such figures. In the US, the post did not formally come into being until Dwight Eisenhower named Sherman Adams his Chief of Staff in 1953. With the exception of Lyndon Johnson, every president since has had a titular chief of staff.

Most have been extremely powerful: a Washington joke of the 1950s has one Democrat saying to a friend how terrible it would be if Eisenhower died and the Vice-President Richard Nixon became president. Not as terrible, the friend replies, as "if Sherman Adams died and Eisenhower became president".

The same might have been said of Al Haig, the former White House Chief of Staff who died a few days ago. Haig went on to be supreme commander of Nato during the Cold War, the head of a major corporation and Secretary of State. However, never was he more powerful than as Nixon's Chief of Staff as Watergate reached its climax.

Nixon, of course, wasn't physically dead. But by the summer of 1974 he was a political dead man walking, as the scandal's tentacles grew tighter round his neck. For several weeks, Haig was effectively running the US government, and managed the transition from Nixon to Gerald Ford – possibly brokering a deal whereby Nixon agreed to resign in return for the promise of a full pardon by his successor.

But few chiefs of staff since have been as visibly and controversially powerful as Rahm Emanuel. He was the first appointment to the new administration, named to the post by Barack Obama on 6 November 2008, two days after the election.

Initially, the choice was praised as a masterstroke; the bulldozing and legendarily profane Emanuel, it was argued, had been a senior White House adviser under Bill Clinton, became a Congressman for a Chicago district, and was widely seen as a future Speaker of the House. As such, he would be a perfect foil for a green and rather cerebral president-elect. Unlike Obama, Emanuel was a creature of Washington, who knew how both ends of Pennsylvania Avenue worked. But the lustre has worn off. Far sooner than expected, there is talk that Emanuel's days are numbered, that he won't even make the two-and-a-half-year average.

Some chiefs of staff, such as Andrew Card under George W Bush, quit from exhaustion. Others, such as Mack McLarty, Bill Clinton's first, have been nice people but unsuited to the job. Yet others are felled by scandal: Sherman Adams, for instance, was forced out after accepting gifts from a businessman under federal investigation, while Bob Haldeman, Haig's predecessor, was thrown overboard during Watergate. Then there was John Sununu, the abrasive chief of staff to the elder Bush, who was found to have taken federal limousines from Washington to attend stamp auctions in New York.

An Emanuel departure would not neatly fall into any of those categories. The fortunes of a chief of staff rise and fall with those of his boss, and now is no exception. As the Obama presidency has encountered rough waters, so has Emanuel.

First came the grumbles, that Obama's circle of advisers was too small. The complaint is not new. Haldeman and Nixon's adviser John Erlichman formed a "Berlin Wall" in the White House, while Jimmy Carter was said to be over reliant on his own "Georgia mafia". Today, the supposed culprit is a perceived "Chicago mafia" led by Emanuel.

Last weekend saw stage two: an article by a respected Washington Post columnist, seemingly planted by Emanuel supporters, maintaining that Obama veered off track because he ignored his Chief of Staff's advice in several specified instances. When feuding in the White House goes public, stage three invariably follows and heads roll. The question is, will Rahm Emanuel's be one of them. And if so, when?