Leading article: A politician who gambled - and lost

Mr Blunkett believed the rules did not apply to him. This arrogance meant he walked a political tightrope

It takes a certain arrogance to gamble. And Mr Blunkett is certainly guilty of this. Last year, when embroiled in a scandal over a fast-tracked visa, Mr Blunkett was revealed to have made disobliging comments about his Cabinet colleagues. This cost him support and hastened his exit from the Government. Yet he failed to learn from this experience.

This summer, following his reappointment to the Cabinet, he briefed journalists that he was effectively "in charge" while the Prime Minister was on holiday. This won him a rebuke from the Deputy Prime Minister, John Prescott.

What both of these incidents demonstrated was Mr Blunkett's belief that, so long as he was unswervingly loyal to his leaders, the conventional rules did not apply to him. This arrogance meant he walked a political tightrope. Yesterday, Mr Blunkett fell off.

The claim by the Prime Minister that his colleague leaves office "without a stain on his character" is simply risible. Mr Blunkett broke the ministerial code of conduct. If he had remained as Work and Pensions Secretary, he would have tainted the entire Government. And Mr Blair must surely know it. Mr Blunkett claims it was he who made the decision to resign. Many suspect that it was actually made for him.

The political future for Mr Blunkett now looks somewhat bleak. A second return to the Cabinet is extremely unlikely. Mr Blunkett must try to rebuild both his professional and private life away from the centre of power. This may be a good thing for him. We are told Mr Blunkett has financial difficulties, brought on by a costly paternity battle. Being removed from the media spotlight should allow him the space to sort out his personal affairs. We certainly hope it will.

Mr Blunkett leaves behind a reputation for having been a formidable politician. He rose to the top despite the odds being stacked against him. He can be said to have overcome not just his blindness and poverty but also his political background. Mr Blunkett began his career on the left-wing Sheffield council in the 1970s, known at the time as the Socialist Republic of South Yorkshire. His political journey from far left to political centre mirrored the resurgence of the Labour Party over the past two decades. Having served as a key member of the Cabinet almost continuously since 1997, Mr Blunkett was a figure of considerable influence. He was even spoken of, at one point, as a potential prime minister.

But his record of achievement in office has been less distinguished than his record as political operator. As education secretary, Mr Blunkett made mistakes, one of which was to close many special needs schools. Yet Mr Blunkett did much good in his education brief, too. Driving up standards in literacy at primary school level was his conspicuous achievement.

He was an awful home secretary. Mr Blunkett's tenure there was characterised by illiberal, draconian and badly drafted legislation. He became notorious for pandering to the prejudices of the right-wing press on sensitive issues such as crime, immigration and terrorism. His taunting of "the liberati" and "airy-fairy libertarians" was unworthy of a minister in one of the great offices of state. It is to be hoped that ID cards - a scheme set in motion during his time at the Home Office - never becomes a reality.

Mr Blunkett leaves his work and pensions brief without having made a mark. This is an area which will be of critical importance in the coming years. A White Paper on incapacity benefit is pending. The debate about the future of the pensions system is heating up. John Hutton, his replacement as Work and Pensions Secretary, has a formidable challenge on his hands.

This will be a testing period for the Government. Yesterday's resignation comes as Tory fortunes appear to be reviving. David Cameron, should he be successful in the Conservative leadership election, looks capable of mounting a serious challenge, especially if he is joined on the front bench by the likes of Kenneth Clarke and William Hague. Many of the Cabinet's heavyweights are fighting among themselves. The intense interest Mr Blunkett's fall has generated is partly an indication of how few true Blairites there are left in the Cabinet. Many ministers are openly positioning themselves for an anticipated transition of power to Gordon Brown before the next election.

Mr Blair himself is engaged in a scramble to secure his own legacy as Prime Minister before he leaves office. He wants to accelerate the pace of reforms in the NHS and, as we saw last week, in schools. He is right to do so. But there is a danger that he has left it all rather late. The public services will require a good deal of the Prime Minister's attention over the coming months if he is to see any his radical reforms actually implemented.

To this end, Mr Blair should stop agonising about peripheral issues such as "respect". The battle over the proposed anti-terror laws should also be brought to an end. The depth of hostility to these innovations was demonstrated in yesterday's Commons vote. Instead, Mr Blair should focus on responding to global warming and rebuilding Britain's links with Europe. Taking a lead in nuclear disarmament would also help secure his legacy. But, inevitably, Iraq hangs over everything. Even Mr Blair must be beginning to fear that this will be what he is remembered for.

This is a precarious time for the Prime Minister. The departure of Mr Blunkett is a serious blow. The Opposition is waking up. Time is running out. There is now a real risk that Mr Blair's third term will deliver nothing of substance. But, despite everything, Mr Blair remains in control. This could be the moment that will break ­ or make ­ Labour's historic third term in office.