Mr Blair may survive Hutton, but the Labour Party is losing faith in him

If Mr Hoon were to decide he is soon to be ministerial toast and chose to cut up rough, he could make Mr Blair's life very difficult

John Scarlett, the chairman of the Joint Intelligence Committee, spent the bank holiday yesterday in his Whitehall office. I know this at first hand because, when I signed the minicab docket after being returned home from a Sky News interview outside the Royal Courts of Justice, I noticed that the previous passenger's signature was that of Mr Scarlett - who was collected by my taxi driver from his home at 8am and driven to the Cabinet Office.

Mr Scarlett was presumably preparing for his evidence, later today, and was no doubt trawling through Alastair Campbell's testimony to the Hutton inquiry to make sure that the two of them are not singing from different hymn sheets. Most observers expect Mr Scarlett to corroborate Mr Campbell's claim that the JIC had "ownership" of the September dossier, and that there was no last-minute "insertion" by Downing Street of the 45-minute claim about Iraq's alleged weapons of mass destruction. But it will still be intriguing to get Mr Scarlett's take on how he viewed the 15 occasions on which Mr Campbell communicated with him to suggest drafting amendments to the document.

It is less easy to know just what choreography, if any, there may be between Geoff Hoon and the Prime Minister when they give their separate testimonies later in the week. It would be revealing if we could also see what e-mail traffic there has been between these two - indeed among all the participants appearing before Lord Hutton - over the past few days. Perhaps one of the minor consequences of this whole affair is that there will be a greater reluctance by politicians and officials to commit thoughts and instructions to computers and inter-departmental memos.

Mr Hoon is expected to have the most difficult questions to answer since he is already on written record as having refused the advice of Sir Kevin Tebbit, his permanent secretary, not to allow Dr Kelly to testify before the Foreign Affairs Select Committee. There is already enough documentary evidence available on the Hutton website to enable the Prime Minister to reinforce the line that he wanted the matter of publicising Dr Kelly's name to the press to be dealt with by the Ministry of Defence. There is also Mr Hoon's incriminating comment that, for "presentational" reasons, he decided to over-ride his chief official. So far, it looks as though Downing Street's strategy is to shift the blame on to Mr Hoon.

But if Mr Hoon were to decide that he is soon to be ministerial toast and chose to cut up rough, he could make life very awkward for Mr Blair. There is also compelling evidence to show that in the crucial meetings in Downing Street, attended by senior officials and Mr Blair, the Defence Secretary was out of the loop - he was not present. Mr Hoon could, therefore, make a convincing case that he was simply carrying out orders handed down to him from above.

Rumours abound that if Mr Hoon accepts the role of sacrificial lamb he might be suitably rewarded in the future. This happened to Leon Brittan after the Westland affair in 1986. He was, similarly, unfairly made to bear the brunt of the fall-out; and the guilt Margaret Thatcher felt about the way he was treated accounts, largely, for his subsequent appointment as a European Commissioner.

Mr Blair's appearance before the inquiry on Thursday is being trailed as the highlight of the week. I suspect that it may turn out, however, to be a bit of a non-event. He will be briefed up to the eyeballs and, having six years of regular experience appearing before the Commons, he is well versed in the art of answering, not answering, and evading difficult questions. It is even possible that he could turn on the sort of tear-jerking performance that served him so well when he responded to the death of Princess Diana. But the reversion to the "I'm a pretty straight kind of guy" line will not work. Contrition will be needed by the bucketful, now that it is patently obvious that public opinion no longer accepts that Mr Blair's government is "whiter than white".

But, perversely, this could be Mr Blair's first opportunity to turn the tide of public opinion in his favour. The latest polls about trust reveal intriguing attitudes towards Mr Blair and his government, with most people blaming Mr Hoon, rather than Mr Blair, for Dr Kelly's suicide. Mr Blair's main problem appears to be more with his party and Labour voters, rather than with the general public as a whole.

The latest ICM polls reveal extraordinary contradictions. On the one hand the Labour lead over the Tories actually has increased, from 2 per cent to 5 per cent, during the course of the past month - precisely the length of time that has elapsed since Dr Kelly's death. On the other hand, more than half of Labour voters in the last general election have turned against the Government. This gives added significance to the forthcoming by-election in Brent East, where 63 per cent of voters supported Labour in 2001.

The safer the seat, the more panicky the party. Labour activists say that anecdotal evidence suggests that Mr Blair is the main problem for Labour voters, rather than for swing or floating voters. Most party supporters were against the war in Iraq, and have therefore been more willing to focus sympathetically on any authoritative voice, such as Dr Kelly's, that questioned the evidence used to justify the war.

So it is likely that Mr Blair will run into bigger trouble from the constituency party management committees, from the party's National Executive Committee and from the party conference, than he will from the wider electorate - or from the slumbering Tory party. Labour MPs are reporting gruesome experiences when they appear before their local parties. Michael Connarty, the Labour MP for Falkirk East, has vividly described the despair among his grass roots supporters. This will have a debilitating effect when MPs gather together, in a fortnight's time, when Parliament returns for its new pre-conference session.

Mr Campbell may have ensured that the machinery of government has thrown a ring of protection around Mr Blair in preparation for the evidence he is to give on Thursday, but there is less Parliamentary Labour Party willingness to do the same - apart from the dwindling band of sycophants who still believe that promotion depends on trotting out the Downing Street lines. Cabinet ministers may now be thinking that the future belongs to Gordon Brown rather than Mr Blair. And there are, once Mr Hoon bites the bullet, few true Blairite believers left. Even in the lower ranks, loyalists such as Yvette Cooper and David Miliband may reckon that, by the time their aspirations to the Cabinet are finally achieved, there may be a different incumbent in Number 10.

So far, Labour MPs have calculated that their futures depend on loyalty to Mr Blair. But the political terms of party trade are likely to change soon, with Mr Blair's future being much more dependent on Labour MPs than on public opinion.

mrbrown@pimlico.freeserve.co.uk