Perhaps it was the demonstrations that twice interrupted his keynote conference speech.
By Nick Assinder
BBC News Online political correspondent in Brighton
Perhaps it was a deliberate attempt to play down the theatrics in favour of a more solid, thoughtful attempt to look towards an historic third Labour government.
Or perhaps something of the old Tony Blair has been lost over the past year.
But the prime minister, who once transfixed this conference even during his bleakest hours, never really hit his stride and looked genuinely thrown by the interruptions.
Protesters aside Mr Blair was well received
This was certainly the speech where he finally admitted in front of a Labour Party audience: "The evidence about Saddam having actual biological and chemical weapons, as opposed to the capability to develop them, has turned out to be wrong."
And it will be remembered for that, at least.
It will also be remembered as the first Blair conference speech to be interrupted twice by hecklers - a sole anti-war protester and a small group of pro-hunt activists - who had broken through unprecedented security to vent their anger.
But, if the prime minister is hoping this is the speech that will be remembered as the turning point away from those deep troubles and towards a more optimistic, pre-election atmosphere dominated by domestic issues, he will almost certainly be disappointed.
There was an almost oppressive security presence both outside the conference centre and inside the hall itself, with guards lined up outside to deter a mass demonstration by the pro-hunting lobby and in front of the platform facing the audience like police facing a football crowd.
It was also another of those swelteringly hot occasions where even the most ice cool would have broken into a sweat.
It was difficult not to form the impression of a conference under seige. That made it equally difficult not to perceive a prime minister also under siege.
But that was why he was here. To "deal head on", as he said, with the issue which has split his party and the country and led to a breakdown of trust in his leadership.
Equally he was here to map out the way forward to a "progressive third term mission" by offering ten commitments to Britain's hard working families.
And he wanted to remind his party just where they stood: "In a position no Labour Party ever dared to dream of standing before - with a third term Labour government becoming."
He flatly refused to say sorry for his actions over the war, despite pre-speech rumours that he was going to use the "s" word.
Instead he again insisted he "believed" he had been right - another of those appeals to have faith in his judgement which have brought criticism in the past.
He also continued with his subtle shifting of the ground over the war by stating he could never apologise for removing Saddam.
Yet, his critics argue, regime change had specifically not been a war aim - largely because it was believed it may have been illegal.
He also seamlessly moved from a justification for going to war on Iraq into a section on the conflict on global terrorism, although his detractors also insist there was no pre-war link between the two.
But the section of his speech that was designed to move things on - his 10 point programme for the next general election manifesto appeared not to have set the conference alight.
It was immediately noted that, while he failed to out-perform Gordon Brown, he also received a reception that was only comparable to the chancellor's, rather than notably better.
Maybe this low key approach was a deliberate tactic. Perhaps it was an attempt by the prime minister to appear more in touch, less distant and lofty.
He certainly did what many of his supporters have been demanding by concentrating on the wider, home-based agenda on pensions, child care, families, education and law and order.
Whether it will mark that turning point away from division and towards a united, forward-looking election campaign is another matter.