But Mandelson's resignation does not have such immediately beneficial effects for the Prime Minister as it does for his political Svengali. (Robinson's resignation, on the other hand, can only help Blair.) Mandelson had nothing to lose by his self-sacrifice. It may cost him a year or two, but as he does not expect ever to be Prime Minister, he has no particular need of time. In return, he has established himself as a man of unparalleled honour, integrity, loyalty and principle. As I wrote when he was humiliated by Labour activists denying him a place on the party's NEC, it is a measure of the man that he is at his best in adversity.
But this is small comfort to Tony Blair. And the way media coverage of Desert Fox turned against him serves as a reminder that, of all years since he became Labour leader, 1999 would be more easily confronted with his ideological and strategic lodestar - Mandelson - firmly fixed amid the twinkling heavens.
Blair's first 20 months in office have been staggeringly successful, but last week's events will serve to remind him, to paraphrase that irritating song, that Things Can Only Get Worse. At the beginning of last week, he counted in the bombers from Iraq, standing on the metaphorical Tarmac and clapping each one of our brave boys on the back as they wound their weary way to the Mission Debrief at Top Secret Command and Control Centre. It's always difficult for politicians to get the balance right between not wanting to seem like civilian geeks claiming undeserved credit, and making sure they get a good slice of the glory. But the PM seemed at first to have got it about right. He was proud of the British lads, tough on Saddam, deeply regretful that such measures were necessary, and the staunchest imaginable ally of the good ole USA. And then, with no warning, the whole thing exploded in his face like a critically malfunctioning Tomahawk Cruise missile with the latest Mark 4 titanium alloy warhead. Bang. The UN was up in arms, the cross-party consensus was dissolved, and 200,000 Guardian readers wrote in to the PM radio programme to say that the Prime Minister's illegal action made him an evil, murdering butcher, no better than Colonel Gaddafi. Even the Daily Mail turned against Desert Fox. Blair was left scratching his head, wondering what the hell had happened. The hardest part for him to swallow was the knowledge that it would have been worse if he had taken the other route. Given that the Americans had their hearts set on air strikes, there were only three options for Blair: he could muster what modest appetite he has for war and give the Americans the diplomatic cover they sought; he could imitate France and Italy in condemning the bombardment; or take the German line, "Go ahead by all means, but you are on your own". The first course of action chose itself.
If Blair had given his full support to the Americans but declined to offer British forces, he would have been crucified by the right-wing press, whose approbation he cherishes. It would have been "Britain's Shame - White Feather for Blair as America Faces Saddam Alone" in the Mirror, and "What Are yEU Frightened Of? - Blair Skulks with Euro-Pals as Yanks Sock It To Saddam" in the Sun. The Tories would have had a field day comparing Blair's weakness with the iron resolve shown by his predecessors. And the US Democrats, with whom he has a slightly over-reverential relationship, would never have forgiven him.
Not that the Prime Minister or his Government have been particularly damaged by the way the tide turned against Desert Fox. The point is that Blair made the right tactical choice and the story still turned sour. It will have been an unfamiliar, rather unsettling experience. The year in prospect will do nothing to dispel those feelings. Governments - even popular ones - conventionally become unpopular in the middle of a Parliamentary term. They do badly in elections held at such times. Yet Labour has arranged things so that next year will be one long act of suffrage. There will be European elections, local government elections, elections for the new Welsh, Scottish and London institutions. And Labour is bound to fare relatively badly in all of them.
The last Euro-elections, held during the depths of Majorism, brought Labour an unprecedented haul of seats. Under the PR voting system next year, the number will be cut in half. In the Welsh Assembly, Labour is certain to win power, but possibly under the leadership of the anti-Blairite maverick, Rhodri Morgan. In Scotland, Labour will probably form the government, perhaps with an overall majority. Or the opinion polls may be right, and Alex Salmond may be the first SNP Prime Minister of Scotland. In which case, Blair will go down in history - at any rate if the Sun has anything to do with it - as the man who broke the Union.
Whoever's cabinet it is, it will come under immense pressure to interpret the untried institutional relationship between London and Edinburgh in the most demanding, difficult and Scotland-centric ways. In local government, the best Labour can hope for in the foreseeable future is not to lose too many seats or too many councils.
Tony Blair will inevitably spend a certain portion of next year barely recovering from one election blow before he is landed with another. And the Euro will put terrific pressure on Labour from the day it is launched. Even though the UK has indicated it will almost certainly not join until after the next election, the British position - "let's see if it works" - will become more and more unsustainable as every passing month shows that it does work. Furthermore, British isolation and the extent to which the national interest has already been damaged by our refusal to join will become increasingly apparent.
All this will be set against an unpropitious background: a House of Lords which has issued a UDI from the Parliamentary Conservative Party, casting government business in doubt; a legislative programme nevertheless packed with controversial measures; an economic outlook which is uncertain to say the least; and an ongoing war between key members of the government.
The past terrible week heralds what is bound to be an arduous year. None of these challenges are insurmountable. And they do provide Blair with an opportunity to prove his mettle as an administrator as well as an election winner. But the cheering crowds and presidential smiles seem destined to give way to gritted teeth and furrowed brows. 'Twas ever thus.
Sion Simon is Associate Editor of `The Spectator' and a `Telegraph' columnist.