The scenarios that could change the face of the Tories

In a spectacular fall from political grace, Iain Duncan Smith's leadership is on the brink, less than a month after the relative success of the Tory conference.

He averted disaster by producing a flat, but gaffe-free, Commons performance yesterday. But such is the crisis besetting the Duncan Smith team that they can only plan from week to week.

Attention will focus on how their man rises to the far more daunting challenge of responding to the Queen's Speech on Wednesday, when he will have to think on his feet, rather than rely on rehearsed questions.

With the next six months holding the key to Mr Duncan Smith's fate, Tory MPs are now speculating on a range of scenarios for the survival – or otherwise – of their leader.

New leader by Christmas

Although yesterday's Prime Minister's Question Time appearance passed off without disaster, Mr Duncan Smith flops spectacularly in his big test next Wednesday in responding to the Queen's Speech. He appears nervous and wooden in contrast to an ebullient Tony Blair, who is roared on by his troops.

His flop follows dismal opinion ratings over the weekend. Within hours the Tory plotters are in overdrive, knowing Mr Duncan Smith will not walk the plank willingly. The 25 signatures needed to force a leadership contest are collected easily, mainly from Tories with majorities of less than 3,000.

Kenneth Clarke, who won the backing of most Tory MPs in last year's leadership election, is persuaded to have one final crack at the job. Michael Portillo and his loyal band of modernising admirers come on board.

Old distinctions of left and right are soon forgotten by MPs, who concentrate instead on who is most likely to save their seats at the next election.

Mr Duncan Smith fights a spirited campaign, arguing that he has not been given long enough to see through his masterplan for reviving the party. Supporters also point out that their man was the clear choice of the Tory grassroots last year.

But it falls flat alongside Mr Clarke's bluff charisma and is finally finished off by polls showing most voters prefer him to the incumbent.

Mr Duncan Smith is soundly beaten and bitterly vanishes into the shadows. The scene is set for a new battle for the soul of the party between Kenneth Clarke and David Davis – or for the rivals to agree to swallow their differences and avoid a gruelling leadership contest by choosing a unity successor.

New leader after May's elections

Mr Duncan Smith stumbles on through his immediate crisis, aided by a better-than-expected performance on Wednesday. Although backbench dissatisfaction with the leader is virulent, it is unfocused, with little clear idea of a strategy for removing him.

Mr Duncan Smith's position is also shored up by Tory associations pleading with their MPs to lower the temperature at Westminster, warning them that the in-fighting is aggravating their problems in winning back reluctant voters.

However, any brief respite over Christmas for the Tory leader ends with the return of MPs to Westminster and the refusal of the opinion polls to budge, with the party still stuck around 30 per cent.

The gloomy polls are translated into real votes in May's local elections, the biggest test of the party's popularity since the last general election.

Although the Tories are already playing down expectations of success, they should expect at least 500 gains if they are to continue harbouring dreams of a return to power nationally. Instead, they achieve only a fraction of that, or even go backwards.

Tory MPs – including Mr Duncan Smith's right-wing soulmates – who believed their seats were safe for life begin to think the unthinkable: that they could be out of a job after the election expected in 2005.

Confidence in Mr Duncan Smith ebbs fatally away with the rising of the sun on Friday 2 May. The only question remaining is whether he resigns before the signatures required to trigger a leadership challenge are gathered.

Duncan Smith fights on until 2005 election

Immediate questions over his leadership are swept aside by an unexpectedly impressive turn on Wednesday mocking the contents of the Queen's Speech. Fickle Tory MPs rally behind him, just a week after they were queuing to lambast his shortcomings.

The feared opinion poll meltdown fails to materialise, with the voters appearing to show less interest in Tory feuding than in problems with their schools, hospitals and trains.

The guns of rebellious MPs are spiked and the plotting fades away, not least because Michael Portillo has categorically ruled himself out of the running, Kenneth Clarke will only accept the job by coronation rather than election and both David Davis and Theresa May are locked into the current leadership team.

A relieved Iain Duncan Smith enjoys the festive period and when MPs return in the New Year, the political attention has shifted to Government woes, including the threat of an economic downturn.

He manages to turn the focus onto Tory policies on health, education and transport, and the party performs strongly in May's local elections, winning as many as 1,000 council seats. The strong showing allows Mr Duncan Smith to argue credibly that the party is finally beginning to bounce back after five years of electoral misery. It also reassures nervous Conservative MPs that they may not be an endangered species after all.

His position is assured and backbench critics fall back into line. Mr Duncan Smith sees his leadership strategy through to the next general election. The upheavals of November 2002 are long forgotten.