YESTERDAY marked the darkest day in Conservative history. In its precipitous decline of the past five years, the party that was once the most efficient electoral machine in the democratic world has lost two landslides and whittled itself down to a rump of just 163 MPs.

Now a quarter of those can no longer bring themselves to support their leader.

Or perhaps it is more accurate to say that yesterday was the darkest day in Conservative history "so far". The day ended with Iain Duncan Smith clinging to power by the very skin on his teeth - saved, for the time being, by a lack of a successor. In all likelihood, there is a darker day somewhere on the near horizon when he becomes the third leader of the once natural party of British Government to lose his job in five years.

Mr Duncan Smith's decline has been as precipitous as his party's. He's been leader for 14 months - a difficult 14 months as he has struggled to make any impact since September 11 understandably overwhelmed his entry onto the national stage.

He staggered unconvincingly into the party's conference only three weeks ago where his "quiet man" speech was well-enough received for the knives to be put down, if not away.

In fact, the Conservatives left Bournemouth in better heart than they had hoped for. All the old ghosts had been laid to rest - the Edwina Currie and John Major coupling had indeed proved to be just a bad dream - and following Theresa May's extraordinary speech in which she labelled her own party as "nasty", Mr Duncan Smith did enough to suggest he was making the Conservatives "more caring and modern".

Yet in doing so, Mr Duncan Smith was falling into the trap that accounted for William Hague 14 months earlier. When the Richmond MP became party leader, he set out to be modern and forward-thinking - he even wore his baseball cap back to front to show how young and daring he was.

This, though, did not appeal to traditional Tories and slowly Mr Hague was forced onto their right-wing ground. As the 2001 General Election approached, the country had its mind on the state of the public services while Mr Hague raged against the euro and asylum-seekers in a desperate bid to persuade tradition Tories to vote for him.

BUT Mr Hague's inability to know if he was right-wing or a modernising leftie left him looking as if he didn't know his own mind.

Mr Duncan Smith has done the same thing. He was elected by the right-wing of the Conservative Party - the traditionalists, the Blue Rinses and what Mrs May would call the "nasty" wing.

Yet Mr Duncan Smith makes nice noises about the party becoming modern, inclusive, caring and cuddly. This has made his right-wing powerbase uneasy and so, to show his credentials, he decided to impose a three-line whip on Monday night's vote over amendments to the Adoption and Children Bill. Never has there been a more old-fashioned Tory rallying point than defending marriage against the wishy-washy liberals who would overwhelm it by allowing co-habiting couples - and worse still, gays - adopt children.

But never has there been a more shaky three-line whip.

Co-habitees of any sexual persuasion are already allowed to adopt children. They can do so as individual people, but not as couples - the Bill merely tidies up this anomaly.

Although the gay rights lobby does regard the Bill as important in its battle to establish gay relationships as equal to heterosexual ones, the principle that gay people can adopt has already been established in law. There was no moral high ground for Mr Duncan Smith to defend.

And Mr Duncan Smith must have known it, for no sooner had he imposed his whip than he let it be known that if MPs didn't like it, they could find a convenient excuse to absent themselves from the House when the vote took place. This was at odds with the most celebrated passage in Mr Duncan Smith's Bournemouth speech where he said: "If I say a thing I mean it. If I settle on a course, I stick to it." But if you happen not to be here, I'll overlook it.

But it goes deeper than this. Mr Duncan Smith is currently touring the country promoting himself as a champion of the vulnerable - he is scheduled to come to the North-East on Friday. There are few more vulnerable people than the 5,000 children in council care, but the Tories championed them by voting to make it harder for them to be adopted.

And it was an utterly pointless three-line whip. The Bill's fate lay in the hands of the Government's overwhelming majority and a far more relevant opposition was in the House of Lords, which last night passed it.

So without any pressing Parliamentary purpose for the Tories, the only point in making such a fuss - by imposing a whip on an issue of conscience which normally gets a free vote - was if Mr Duncan Smith wanted to appeal to the right of his own party.

This bungled attempt at leadership was followed by an equally bungled charade yesterday. Mr Duncan Smith came out with a statement so weak it made John Major look positively heroic. "The party will not look kindly on people who put personal ambitions before the interests of the party," said Mr Duncan Smith limply. He did not have the courage to follow Mr Major into the Rose Garden to fight his opponents in a bloody leadership battle; he did not even have the courage to follow Mr Major into withdrawing the whip from the rebels.

He did not even have the nous of Mr Hague to understand what was happening around him and quietly quit. One of his rebellious backbenchers coined one of the year's great quotes when he said Mr Duncan Smith was "murally dyslexic" - unable to read the writing on the wall. Instead, the leader said his party must "unite or die". After Monday night's vote, it is clearly disunited - therefore it must die.

AT Westminster, there is now a feeling that the Tories could follow the Whigs of the 18th Century and disappear. Or they could split into two: a rump of right-wingers following deputy leader David Davis, and a gaggle of modernisers from Michael Portillo's camp following Shadow Home Secretary Oliver Letwin. This would be extraordinary. It would be real political history.

But the Tories can't even muster one decent candidate to replace Mr Duncan Smith - therefore their finding two is unthinkable.

Mr Portillo has too many enemies within the party and the media to make him a credible candidate; there is talk of him joining forces with Ken Clarke on a dream ticket, but Mr Clarke is probably too old and certainly too European to be acceptable. Theresa May is the bookie's favourite but utterly anonymous except among those who confuse her with her pornstar namesake. Mr Davis is too arrogant to be a leader and Mr Letwin has a habit of making mistakes like getting comically caught on camera in a Roman gladiator's outfit by popstar Billy Bragg.

No wonder bookmakers yesterday took a bet on Mr Hague at 100-1 becoming the next Tory leader.

This lack of options is Mr Duncan Smith's saving grace. And whichever alternative takes his place, the same problem will stare them in the face.

This is still a party that doesn't know where it is going. It is a party that doesn't know which century it stands in - 19th or 21st. It is a party that doesn't know whether it is still trying to conserve John Major's old maids who cycled happily to chapel averting their eyes from all of life's difficulties and awkwardnesses, or whether it is trying to grapple with a modern life where unmarried couples, be they straight or gay, are accepted with only a flicker of an eyebrow.

This was best summed up by a speaker at this year's party conference in Bournemouth: "We must first understand the way life in Britain is lived today, and not the way it was lived 20 years ago."

The speaker was Iain Duncan Smith. But at the first opportunity to show he was beginning to understand modern life, he looked the other way. Instead he imposed an indefensible three line whip that incited rebellion and has condemned his party to many more long dark days with no prospect of a dawn in sight