'INFAMY, infamy, they've all got it in for me" - as he vowed to face down his enemies, Iain Duncan Smith was flanked by four of his most trusted lieutenants - lieutenants who, if rumours are to be believed, would be only too happy to step into their leader's shoes, if not plunge the knife in themselves. It cannot have been reassuring to know his back was so exposed.

For the steps of the Senate, read the steps of Tory Central Office; for Julius Caesar read IDS; for Carry On Cleo read Carry On Conservatives. Her Majesty's Opposition is doing its best to recreate the best traditions of British farce.

But presumably IDS did not have this in mind when he threw down his challenge to the plotters and schemers. After six weeks of speculation and whispering, the previously Quiet Man went into attack mode and decreed it was time for his enemies to put up or shut up. Unfortunately for him, they chose to put up.

By tonight, his fate will be sealed. Whether he is to fall under the blows from his many assassins; or whether he is to limp away, wounded but still bearing that laurel wreath on his polished crown. Such is the mounting discontent among Tory MPs at his leadership, even if IDS wins today's confidence vote - which itself seems far fetched - it can only be a temporary reprieve.

And it is not hard to see why. IDS was never the choice of MPs: in the first ballot to succeed William Hague, he polled only 39 votes out of a possible 166, and even though he pushed Michael Portillo into third place in the final ballot before party members had their say, he was still a poor second to Kenneth Clarke.

It was among the Eurosceptic constituencies that IDS found his strength: his relative anonymity combined with distrust of Clarke's enthusiasm for the euro handed him a decisive victory. But if it was the activists who gave him the crown, the idiosyncrasies of the Tory leadership rules dictate that it is MPs who can take it away.

From the start, IDS's reign seemed fated. The declaration of the result was postponed and a glitzy party cancelled out of respect for the victims of the September 11 tragedy, and the new leader never seemed to recover momentum from this inauspicious beginning.

A halting and unconvincing Commons performer, he has been unable to match his predecessor at besting Tony Blair at Prime Minister's Questions and frequently provides only frustration instead of inspiration to the backbenchers behind him. Similarly, his efforts to connect with the public often fall flat. In encounters with the voters, he appears awkward and ill at ease, with none of the casual confidence of a Blair or Hague.

Earlier this year, he put himself through special training to become a more effective public speaker: learning how to use his hands to make his point and to move about the platform to hold his audience's attention. The result was the embarrassment of this year's conference speech, when the concentration behind every supposedly spontaneous gesture was written all over his face, and whoever decided a lectern in amongst his audience was a good idea had reckoned without a speaker as wooden as IDS. His reputation as having the charisma of a dunked digestive is well deserved.

To his supporters, of course, he is unlucky. Unlucky to be pitted against such a born - if sometimes hammy - performer as Blair, and in charge of a party riven by personal rivalries as the Tories. To them, his successes in calling a halt to divisions over the euro and in coming up with a new set of policies have been overshadowed by the carping of those who have never accepted the result of the leadership election. It is hard to escape the conclusion that there are some MPs who never wanted IDS and will be damned if they're going to put up with him.

But in the end, IDS's biggest crime, and one for which he may well pay the price today, is that the Tories look no more likely to win the next election than they did two years ago. Despite a Government which has failed to deliver and is bumping up taxes, has been deeply divided over Iraq and shamed by the David Kelly affair, and has lost both the trust of the electorate and the respect of the international community, the Conservatives are still polling badly.

A poll in the Guardian last week put the Tories on 33 per cent, five behind the Government and staring at a Labour majority of 160. Tory MPs are not the most forgiving at the best of times, but when it comes to their seats there is no room for sentiment, as even Margaret Thatcher discovered. In this scenario, Betsygate - the allegation that he paid his wife to do more office work than she actually did - is more of a distraction than a reason to ditch. A strong leader would have had little difficulty in batting away such trifles.

IDS's followers, and there must be some, may contend that no other leader would do better, but they could hardly do worse, and even if he survives today's vote it seems over-optimistic to think the sniping will cease. A new leader may not win the next election, but he, and it is almost certain to be a he, could give the Tories something to smile about. Until then, as far as Conservatives go, it's Carry On Screaming.