The Week in Politics: Are we hearing the last gasps of a drowning Tory leader?

I have spent most of the past week patrolling the corridors at Westminster in search of Tory MPs and ringing known dissidents who want to bring down Iain Duncan Smith.

In a week when the Commons returned for a potentially difficult session for the Government, with revolts looming on foundation hospitals, university top-up fees and calls for a judicial inquiry into the Iraq war, my week was devoted almost exclusively to the febrile Conservative Party and its beleaguered leader.

Now some people, Mr Duncan Smith included, would argue that I had got my priorities all wrong. True, the Government has had an undeservedly easy ride in the past seven days.

A story from the Hutton Inquiry, confirming that Tony Blair chaired the decisive meeting that led to the unmasking of the government scientist David Kelly, was knocked off most front pages by the turmoil over whether the Tory leader had paid his wife too much when she worked as his secretary. Which really matters more, you might well ask. After an uncomfortable summer, ministers are enjoying a rare spell out of the limelight.

One senior Whitehall official told me: "There are lots of turf wars going on in the Government, but you guys are missing them because you're obsessed with Tories."

True, without the Betsygate affair, the media might have made much more of the widening divide between Mr Blair and Gordon Brown. They are at odds over Europe and pensions, and there was a needless spat between their aides over tax after the Prime Minister committed the sin of giving an interview to The Times, which the Chancellor regards as his house journal. (Surprise, surprise, Mr Brown penned an article for the paper two days later.) The media might also have looked more closely at the split in the Cabinet over David Blunkett's plans for identity cards.

Having said that, the Tory story was real and it deserved its prominence. It is not about whether Mrs Duncan Smith worked 25 hours a week for her husband from her Buckinghamshire home.

The move to oust her husband is no figment of the media's fevered imagination. I bumped into one Tory frontbencher who had just been defending his leader on television. Before I could ask him what he made of the situation, he said: "Don't even ask."

I could not help feeling, as I observed Mr Duncan Smith at close quarters, that I was witnessing the desperate last gasps of a drowning man. The blunt truth is that many of his MPs want to pull him under because they do not believe he is up to the job.

Although there is no agreement on a successor, that might not be enough to save him this time. A dangerous consensus is emerging that, in the words of one former minister: "We couldn't fail to do better under anybody else." So hardline Tory rebels are now trying to win round waverers who don't want Mr Duncan Smith but are worried about unleashing the chaos and bloodshed of yet another Tory leadership election.

The investigation by the Parliamentary Standards Commissioner may have bought Mr Duncan Smith a little time. Although some critics fear an acquittal would strengthen him, it might not be enough to save him, but even a mild rebuke could be the final nail in his coffin. Indeed, some of the "cowards in the shadows," as the Tory leader memorably called them, are hoping the commissioner will do their dirty work for them.

I suspect that Sir Michael Spicer, the inscrutable chairman of the 1922 Committee, has already got a file of letters from Tory MPs requesting a vote of confidence in the leader that runs into double figures.

So the dissidents may well clear the necessary hurdle of 25 names before long. Some senior Tories have urged Mr Duncan Smith to "clear the air" by calling a confidence vote himself, rather like John Major in 1995, but I fear his position is so perilous he could not take the risk.

Although some critics feel sympathy for the way Mrs Duncan Smith has been dragged into the mire, it will not stop them moving against the Tory leader when the investigation is over. Unfortunately, the sympathy factor has been reduced by the way Mr Duncan Smith has responded to the attacks on his integrity.

His performance in media interviews in the past fortnight has been odd. The Quiet Man seems to have had a 10,000-volt shock which has transformed him into a poor man's Arnold Schwarzenegger. I am told he has started to use the F-word a lot in private, and he is not talking about a Federal Europe. In TV interviews, he has threatened to shoot Mr Blair and the Tory plotters. He tried, embarrassingly, to halt a live interview on Sky.

He told journalists in Cornwall to calm down, perhaps advice he should have given to himself. His aides say he cannot help showing his genuine anger at the nasty attempt to smear him.

But I cannot help thinking that I prefer the Quiet Man, because that is the real Iain Duncan Smith.

The other downside of the Tories' trauma is that a weak opposition is in no position to hold the Government to account. Prime Minister's question time on Wednesday, which should have been an opportunity for Mr Duncan Smith, became an ordeal.

He couldn't even throw his usual soundbite at Mr Blair - no one believes a word he says any more - because it would have rebounded on him and raised the spectre of Betsygate.

A feeble opposition is unhealthy for politics. It is even more worrying when we have a government that lacks direction and yet is seemingly coasting to a third general election victory.

That is why I now believe that, sooner or later, enough Tory MPs will decide it is their duty to ditch their leader.

a.grice@independent.co.uk