Matthew Norman: You couldn't make this one up if you tried

I keep hearing the lines in the voice of that much underrated political strategist Liza Minnelli

Whatever other delights the week in Westminster has offered so far - and you'd want a six-volume encyclopedia to catalogue each individual merriment - the one most indelibly branded on the memory comes from the magnificent "Farewell Tour" memo.

That this breathtakingly hilarious document, written by one of Mr Tony Blair's most senior advisers with the full knowledge of the laureate of eye-catching initiatives, was confirmed in the time-honoured fashion on Wednesday by a categorical denial from Number 10. The precise identity of its creator may never be revealed, but whoever came up with the following exhibits a poetic gift that offers an alternative career in musical theatre when its author finally joins Blair in the political wilderness.

"He needs to go with the crowd wanting more. He should be the star who won't even play that last encore." Capturing in a mere 23 words the essence of the clinically insane self-delusion that tends to enliven the closing days in a failing leader's bunker is something in itself. To do so in a rhyming couplet that might have been rejected by Benny and Bjorn, on scansion grounds, from the final draft of "The Winner Takes It All" (or included in a Tim Rice meisterwerk) is nothing less than genius. I keep hearing the lines in my head, in the voice of not Philip Gould, that least charlatan of focus groupies, but that much underrated political strategist Liza Minnelli.

As ever with brutal power politics at their sordid best, it's hard to watch the mayhem without musing on the relevant dramatic comparison. Shakespearean tragedy is the usual template for a morbid power struggle of the kind, and if Gordon views himself as Bolingbroke rising to seize Richard II's throne on a wave of public affection, small wonder that the recent slump in his own approval ratings has drained what little reserves of patience he had left.

Satirical comedy, however unintentional, has always been one of the New Labour Repertory's strong suits, and it gets stronger all the time. The day after leaking to The Sun his intention to go next July, Mr Blair lacerates the disloyal, discourteous Tom Watson for leaking the letter requesting his prompt departure. That night, party chairman Hazel Blears appears on Newsnight and manages, bless her doughty heart, to intone the phrase "stable and orderly transition" without vomiting. The day after, Gordon miraculously relocates his larynx to declare, without the hint of a cheeky wink, that it's entirely up to Mr Blair when he goes. As satire goes, it's pretty crude stuff. Yet somehow it works.

And then, of course, there is soap opera. A while ago, soaps were all the rage, with analysts contemplating the amazing cast of New Labour characters brought low by sexual and financial misdeeds, with the couple at the show's heart often likened to Jack and Vera Duckworth. The marriage has since moved on, alas, the bickering replaced by the sort of poisonous passive-aggressive warfare better suited to kitchen sink drama than Coronation Street.

A really nasty, fetid marriage cannot endure in silence forever, however much its protagonists would rather not raise their voices in front of the kids. The Downing Street screaming matches of Wednesday have been patched over for now, but the twin statements of yesterday - each so vague as to challenge the most nimble Kremlinologist - cannot hold the line for long.

For the couple who decide to separate, but postpone the date for a few months until the children are safely back at school, the most banal irritant - the bath unrinsed, the lid left off the Marmite jar, a trivial coded attack from unnamed sources on page 13 of the Mirror - will burst the dam and unleash another torrent of frothing resentment. Imagine the fresh explosion of backbench panic that will greet the next batch of scary opinion polls or the Met finally feeling the Prime Ministerial collar over the sale of peerages.

Whatever hurried deal Blair and Brown have done, whether written in blood and witnessed by the entire Cabinet, something will very soon crop up to obliterate it. Led by Alan Milburn, a man whose belligerence is matched only by his irrelevance, the self-styled Blairite ultras have determined to wage a civil war that will last a decade and more. Never more than professional oppositionists, sharing their leader's preference for defining themselves by enemies rather than beliefs, they will utterly overjoyed if their vendetta helps land them back in opposition at Gordon's expense

However far Mrs Thatcher's diehard praetorians went to destroy John Major, Messrs Milburn, Byers et al will go further to destroy Gordon Brown. Whether through paranoia or mendacity, or both, they talk of Wednesday's mass resignations as a coup, painting the likes of Chris Bryant and Khalid Mahmood as Brown ciphers when the only thing brown about them are the noses that worshipped Mr Blair for so long. For now, the solitary coup in New Labour history remains the one that saw a tiny, brilliantly ruthless clique of five or six seize control of a political movement no sooner than John Smith's eyes had been shut.

None of this is to suggest that Gordon is blameless with regard to the chaos threatening to cast him in the pitiable role of Anthony Eden, who waited a decade with ill-concealed fury for Churchill to go, and then had less than two years in Number 10. Unquestionably, Gordon has at last won his war with Mr Blair, but the victory seems likely to be as pyrrhic as they come.

Had he shown the courage to take one of several glorious opportunities to finish off Blair before the last election, and then won his own mandate, he might have cleansed the wound of Iraq. Instead, his pathological fear of striking openly permitted that wound to become infected, and the gangrene of public disaffection may already have spread too far for the amputation of Mr Blair to save Labour in time for the next election.

And so, the one too monomaniacal and deluded to accept the bleeding obvious, the other too fretful of the Heseltinian cliché about assassins and crowns to do the bleeding obvious, they limp on, nervily awaiting the next eruption and where it will lead.

Ultimately, in this bizarre and compelling terminal stage of the project, the unfettered queeny hysteria (and no political clique in history has been queenier) seems dramatically best suited not to Shakespearean tragedy, Jacobean revenge, soap opera, the kitchen sink or even high farce, but to musical theatre. Liza with a Zee would make a deliciously faux-brave Cherie, eyes glistening, voice quivering, sharing his refusal to accept the inevitable even to the last, belting out the show-stopper even as the Pickford's truck pulls up outside the door. "He needs to go with the crowd wanting more/ He should be the star who won't even play that last encore."

You'd need sides of stone not to split them at that one.