Fraser Nelson: Enter Dr Reid, the 'contemptibly brilliant' warrior leader

The 100-day curse was one John Reid cast upon himself. He not only suggested that this deadline should be used to judge him in his new job as Home Secretary, but cheerfully declared his head to be "on the block".

Given the disasters that his department was then churning out on a daily basis, it seemed a suicidal gamble. But those who wanted him to fail could not be more disappointed.

The 100th day fell last Friday, as Dr Reid was giving his second press conference on the foiled terror plot. He has played the role of the wartime leader to perfection, dominating television coverage and achieving 10 times as much air time as the Conservatives. One Shadow Cabinet critic snarled that he had been "contemptibly brilliant". This is not a Home Secretary following his four predecessors into the political quagmire.

John Reid is on an altogether different trajectory and one that should greatly worry his old adversary Gordon Brown, who is off nursing his newborn son. It is a macabre rule of politics that the best opportunities lie in the deepest crises. The Home Secretary will emerge from all this a much strengthened figure, far better placed to make his own leadership bid.

All this will please Tony Blair. At No 10, there is still a romantic hope that Dr Reid will somehow rise to take on Brown. The people whom the Treasury now calls "ultras" (i.e. supporters of the Prime Minister) will be delighted that the news agenda has handed him such a platform, topping a convincing debut at the Home Office.

His trick has been to detach his personal performance from that of his department. Declaring the immigration service not "fit for purpose" meant he would be vindicated, not hurt, by its subsequent mistakes. The man who gave up alcohol in 1994 has administered to his department its own 12 step recovery plan: "First, admit you have a problem," it runs. "Then, deal with the problem ..." and so on.

Most of his plans involve conveniently faraway deadlines. There will be 8,000 new prison places (by 2012), the immigration budget will double (by 2010) and the 10,200 foreign prisoners will be deported (at some point). He has axed disaster-prone projects such as the merger of English police forces, and declared the 2008 deadline for the first identity cards an "artificial target".

The Home Secretary's main job is to build up public confidence in the system. Hence his adopting a palatable version of the immigration policy the Tories championed at the last election. It is not racist to discuss quotas on immigration, he says - in a stroke going further than David Cameron's Tories currently dare.

The Conservatives now consider immigration a toxic topic and Damian Green, their immigration spokesman, privately moans that it is his job to say as little as possible. All this leaves the ground open to Labour, and for Dr Reid to pick up where the bombastic David Blunkett left off.

The next task for Dr Reid is to be victorious where Charles Clarke, his predecessor, met defeat. Flushed with the victory of the thwarted terrorist plot, it is entirely possible that he will bring back plans to detain terror suspects without charge for 90 days. With the terror suspects in custody, and the clock ticking on when they have to be released, Dr Reid has the perfect backdrop to renew this case.

Selling unpopular ideas to the Labour Party has become his speciality. As a former Communist, he has been able to couch them in idealistic left-wing language that the Mr Blair would not have been able to articulate. NHS reform was needed, said Dr Reid, because choice should be for everyone not just the rich. But finding a progressive reason for extended detention will be a far harder task.

Last week, in a speech to the Demos think tank, John Reid spoke of the current idea of human rights as forged in a postwar era where a fascist state had been the main enemy. But today, he said, the threat comes "from what might be called fascist individuals" who threaten to destroy equality and the "biggest achievements of democratic socialism". Hence the jihadists are portrayed not just as homicidal fanatics, but as class enemies. Dr Reid is thus wrapping a right-wing goal in left-wing vocabulary.

Herein lies a powerful formula for winning elections. Let us presume that David Cameron's gamble is that he will gain votes from the Liberal Democrats, while right-wingers have nowhere else to go. And for as long as Gordon Brown is leading the Labour Party, with his high taxes and scary five-year plans, this is a fair analysis.

But if Dr Reid were Labour leader, there is an interesting dilemma for the orphaned Conservative voter, who may see in the Home Secretary a strong leader, reliable in a crisis, who pursues a hard line on immigration while calling Islamofascism by its name. In an age where party allegiance has never been weaker, might such voters give the bald-headed, spirited, dependable, sixtysomething a go? As the Prime Minister said in California earlier this month, we live in an age of political cross-dressing. Brown's pitch, however, is that he will restore Labour's "soul", and nine years of stealth taxes have taught Middle England to be wary.

All this is speculation, but the Tory strategy, right down to the choice of leader, is based on fighting a Labour Party led by the familiar figure of Mr Brown. To be up against Dr Reid, who makes daring raids into Tory territory with none of the Chancellor's communicatory handicaps, is a more daunting prospect. Those who want Mr Cameron to be Prime Minister can only hope Labour does not see this for itself.

Fraser Nelson is political editor of 'The Spectator' and 'The Business'