Leading article: The lesson of this week: leaders must be held accountable

WHAT IF it happened here? What if Tony Blair engaged in inappropriate - but consensual - conduct with a junior member of his staff and lied about it in a failed sexual harassment case brought by a different public employee? And what if - a critical consideration, this - the Prime Minister's high public approval ratings were to go up as a result?

It is, of course, an outlandish series of propositions - "just a bit of fun", as the great Peter Snow might say, in front of one of his more unlikely computerised graphic projections of what would happen if there were a post-war record electoral swing. However, it is outlandishness with a purpose, worth pursuing for a moment as a way of testing whether the Senate trial procedure in the US is the right way to hold the chief executive of a democracy to account.

And, of course, it could not happen quite like that, because the American people knew when they elected him that Bill Clinton was a philanderer who was given to slipperiness when pressed about his private life - which explains why the President's popularity has been remarkably immune to the affair - whereas Mr Blair was sold on a rather different prospectus. But what if a British prime minister were in the same situation? How would our system of half-written checks and balances deal with him, or with her?

There would, of course, be no direct equivalent to the process of impeachment and trial through which Mr Clinton is passing. That trial, poised between majesty and farce, seems quite apt for an offence that is on the cusp between an inexcusable lapse by the chief law enforcement officer of the US and, well, nothing at all.

Whereas a British prime minister is subject to a simple majority vote in the House of Commons, the US Congress can eject a President from office only by use of this elaborate constitutional procedure, a hybrid of politics and law. This trial is, as the Democrats never cease to point out, essentially a political process taking the legal form of drawing up the charges, hearing the prosecution and defence cases, and, probably, taking evidence from witnesses. For all the invented solemnity of the procedure, from Chief Justice William Rehnquist's four-striped cloak to the myth that senators will vote as disinterested jurors, it has been conducted entirely on party lines so far.

There is a working assumption in America that a president cannot be tried in court for a criminal offence while in office. This assumption has not been tested in the Supreme Court, but its effect is to leave the checks on the President's conduct to what is ultimately a political process.

Mr Clinton's salvation, therefore, depends on the efficiency of the transmission mechanism between public opinion and the Senate. As long as he remains popular with the American people, it is unthinkable that two-thirds of Senators will vote to remove him from the presidency. So it was with Richard Nixon, who was pursued with equal party political vigour by the Democrats over an initially trivial matter, a "third-rate burglary" that he did not order but which he tried to cover up. However, the voters had fallen out with Nixon, and Republican members of Congress knew that they could not ensure their own re-election if they defended him.

In Britain, on the other hand, if a popular prime minister retained the confidence of the House of Commons, he or she could still face a criminal trial while in office and, if convicted, be immediately disbarred from being an MP. Thus, if Mr Blair were found to have committed perjury, no matter how personal or understandable the cause seemed to most MPs or voters, he would be out. It would seem truer of the ramshackle British constitution than of the American that "no man is above the law".

Indeed, the lessons of the Clinton trial on this side of the Atlantic apply rather more to the recent crisis in relations between the European Parliament and Commission than they do to prime ministerial accountability. As in the US, the European Union's executive is not sustained by a simple majority of its representative assembly, while it is subjected to a long- stop sanction of dismissal by a two-thirds majority.

Worse, though, the Commission is not directly elected, and so the peoples of Europe do not even get the periodic chance to throw the rascals out. Europe needs a system - short of the nuclear option of sacking the entire Commission - for getting rid of leaders who are not up to scratch. We should not mock Justice Rehnquist's cloak too much; after its failure to do so this week, the European Parliament urgently needs to invent some better and more dignified mechanisms for holding our supra-national executive to account.