Mr Blair will remain in office until his place in history is secure

Whatever his other achievements, he cannot yet claim a lasting monument in his own country

If you think there is something new in the chronic tensions between Gordon Brown and Tony Blair, then Democracy, Michael Frayn's enthralling play about Willy Brandt's chancellorship of Germany cannot fail to make you think again. It isn't just the telling complaint by Brandt's ambitious finance minister - and successor - Helmut Schmidt that he is watching his boss, the German Chancellor, let everything the two men had fought for "slip through his fingers." It's also the more mundane moment when an exasperated Schmidt asks: "What's happening to this government? We casually launch into wild schemes without any proper consultation. We take on new commitments without any idea of how they're going to be funded..."

The latter complaints fuse almost perfectly with both Brown's persistent criticism that the policy on top-up fees was entered into wholly without adequate preparation, and his famous first-term gibe that Blair wanted both increased public spending and tax cuts. Just as Blair's past frustration with Brown's silence at moments of crisis finds an echo in the moment when Brandt, facing a confrontation with the public sector unions urged on him by Schmidt himself, exclaims: "No support from Helmut because - no Helmut." Told that Schmidt is away in Washington and asking whether there is any word from him, Brandt is told: "He says - just do whatever you think is best."

Frayn is much too preoccupied in his play with the post-war Germany, which rightly fascinates him, to have intended a parallel with the more mundane circumstances of here and now. I'm by no means the first to point out how his play, currently at The National, nevertheless has a contemporary British relevance. But that's because it reflects so brilliantly the universal truths about government in advanced democracies - the interplay of personality with political ideas and imagination - as well as the peculiarities of the extraordinary period in West Germany between 1968 and 1973.

And in particular those which inform a social democratic government; several commentators - starting with Gerald Kaufman - have pointed to the lament of left-of-centre politicians through much of the 20th century which Frayn puts in the mouth of one of Brandt's lieutenants: "We won. That was our great mistake, Willy. Defeat is the only thing that this party understands. Defeat is a testimony to high ideals. Defeat makes no demands. Victory means you have to do something - and doing something always involves dissent and compromise and making mistakes."

In detail, of course, there are as many contrasts as there are similarities. True, Brandt and Schmidt had led the move to dump the SDP's Marxist past at Bad Godesberg rather as Blair and Brown embarked on the modernisation of the Labour Party. The much loved Brandt connected emotionally with the West German public and even more so with his own party in a way that Blair would never claim to have done. Finally Brandt's second order weaknesses - which included drink and women - were different from Blair's.

That said, Frayn's outstanding play, laying bare a sense of drift in a government of the centre left, is partly an essay in political mortality. Isolation from colleagues, a sense of disappointment about what has been achieved, the presence of a capable and ambitious rival candidate, even anger on the left, have their echoes in some of the problems of the Blair premiership. How dangerous are they?

On the crudest and most extreme reading, a haggard and ageing Blair was drifting towards a possibly terminal crisis in the first half - if not the first month - of next year. Then, lo and behold! Not only is Saddam seized, but Libya's own dictator comes in from the cold and opens up his own Weapons of Mass Destruction to international inspection and destruction. Meanwhile, there are tentative signs that Gordon Brown may, after all, use his considerable influence to ensure that the policy on top-up fees--however hedged with concessions - goes through next month. So Blair could be alright after all.

This snakes and ladders view of political survival matches its cousin, the zero sum approach to any given event in which the prime minister plays a part - particularly, but not only, when Iraq is involved. Libya is a case in point.

On the one hand, several apologists for the war in Iraq haven't hesitated to argue that without it the deal would never have been done. To make this claim stick, you have to explain both how it was that Gaddafi came forward with his proposal before the Camp David summit which preceded the war and the process which led up to it resulted from a long and continuous process of engagement going back to the last Foreign Secretary Robin Cook. Not an easy task - which may be why neither Tony Blair or Jack Straw have explicitly suggested Iraq was the reason for the deal.

Yet the contrary assumption by critics of the war - that the Libya deal shows that a similar one could have been negotiated with Saddam Hussein - seems equally improbable. Sure, Washington may not have wanted negotiations with Baghdad. But it isn't easy to find the moment in the run-up to the war when the negotiations might have taken place even if it had wanted them.

The fact is that whether Blair goes through to the next election and beyond depends greatly, as it always has, on his own political will to do so. Brandt was finally brought down by the unmasking of one of his closest aides as an East German spy - not the kind of problem likely to afflict the British prime minister.

True, Hutton could in theory be bad enough for Blair for him to go. True, his position could be terminally weakened by a defeat on top-up fees. It's even possible - as one or two MPs who would like to see Brown take over before the next election purport to think - that he might even pack his bags after a victory on top-up fees, on the grounds that he could then quit while he's ahead.

And yet the Frayn play prompts one other reflection. For all Brandt's travails, his Ostpolitik - and the outreach to East Germany particularly - was a lasting monument to his chancellorship even if it was not until 1989 that the Berlin Wall fell. Whatever his other achievements, Blair cannot yet claim such a monument in his own country. Even if Iraq finally becomes the peaceful democracy everyone sane wants it to be, this will have been, in the end, Bush's war. Britain's relationship with Europe - among several other things - will not have been consummated in the way Blair sought when he came into office. Human nature normally speaks against walking off the job in such circumstances.

Anyone who says he knows for certain whether Blair will still be prime minister come the election has more courage than sense. But if he isn't, he will have left a good deal more unfinished business behind than anyone - Blair included - could have guessed six long years ago. He, above all, must know this. Voluntary departure, in such circumstances, cannot fail to be an uninviting prospect.

d.macintyre@independent.co.uk