The terrorist threat must never be politicised - even in a close presidential race

Any Government deciding whether to make public a security alert treads the finest of lines. It is damned if it issues the warning and damned if it doesn't. If nothing happens, it is open to charges of scaremongering, while if it says nothing and there is an attack - another 11 September, to take an extreme example - it will be accused, justifiably, of overconfidence, negligence or worse.

Any Government deciding whether to make public a security alert treads the finest of lines. It is damned if it issues the warning and damned if it doesn't. If nothing happens, it is open to charges of scaremongering, while if it says nothing and there is an attack - another 11 September, to take an extreme example - it will be accused, justifiably, of overconfidence, negligence or worse.

Add in to this equation a keenly contested US presidential election, in which national security looms large. Add, too, an increasingly unpopular war entered into, in part, on the basis of faulty intelligence, and the waters become thoroughly muddied. Whichever course officials take risks appearing to have a political motivation, even if it does not.

This is where we are now, and where, regrettably, we are likely to remain until America votes on 2 November. The acrimonious to-ing and fro-ing about the latest security alert, announced by Tom Ridge, the US Homeland Security supremo, on Sunday, is a mere foretaste of the slanging matches to come between the Bush administration and its opponents.

And this time around, at least, the Republicans surely have a case to answer. Maybe it was pure coincidence, but Mr Ridge's warning of new al-Qa'ida plans came just in time to push John Kerry's post-convention road-show out of the headlines and put George Bush back on the screen in full nation-protector mode. It also yanked the political agenda from an incipient discussion of the economy right back to trusty old national security - the one portfolio where Mr Bush's polls consistently higher than his challenger.

The urgent warning for New York also seemed to contradict the local authorities' own assessment of the city's security. The Statue of Liberty was due to be reopened to the public yesterday for the first time since the terrorist attacks of 2001. The ceremonies went ahead as planned, sending a confusing message to Americans about the imminence of any threat.

Compromising the administration's warning further, The New York Times reported that the "new" information cited by Mr Ridge, for all its much-vaunted "specificity", was actually more than three years old. So why, it asked, the sudden, Sunday afternoon alert; all the disruptive emergency measures?

The administration could not leave this unchallenged. Within hours, a White House security official and Mr Ridge were separately back at the microphones, insisting that "some" of the information on the recently confiscated computer had been updated as recently as January. Some, but how much?

Mr Ridge's bigger argument, supported also by Mr Bush, is that no administration can afford not to act upon good quality information as soon as it is received, even if it is old, as it may be evidence of a continuing intent. This is a valid point. If they could bear to refer to former President Bill Clinton, they could also quote the hostile press he received when he authorised a missile attack on Iraq at the height of the Lewinsky scandal. There was a universal suspicion that he was abusing his position as commander-in-chief to mount a political diversion - a suspicion that was, with hindsight, almost certainly wrong.

The current administration is certainly aware of the risk that it will be accused of hyping the terrorist threat to engineer Mr Bush's re-election. This is surely why Mr Ridge supplied so many details. His previous, very general, alert had been greeted with widespread scepticism - the first sign that the White House might have traded on the terrorist threat once too often; the first sign, too, that public fear of a new attack might be waning.

Judging by past elections, the Bush team is not averse to playing dirty, very dirty, in extremis. The question is whether the Bush campaign would dare play the terrorist card to improve the President's chances. And whether, if it did, a sufficient number of American voters would succumb to the fear. We sincerely hope that the answer, on both counts, is a firm no.