Mr Blair will face a deeply sceptical audience today at his party conference, writes Frank Millar, London Editor
Mr Tony Blair and the Labour conference face a moment of truth this afternoon when the British Prime Minister addresses his troubled party for the first time since the Iraq war.
Assuming continuing efforts to force a vote on the issue fail, most Labour insiders are agreed that the defining moment of this conference - and the real measure of his difficulty over the Iraqi conflict - will come with the reaction inside the hall both before and after Mr Blair's speech.
Mr Blair has never faced heckling at a Labour conference, but the competing nightmare for party managers is that a robust defence of the case for toppling Saddam Hussein could be heard in silence by large numbers of representatives still deeply suspicious of the government's case for war and hostile to Mr Blair's alliance with President Bush.
Mr Blair's big test comes just 20 hours after a barnstorming performance by Chancellor Gordon Brown with a speech inevitably seen as that of a potential future leader whose biggest current problem is not a lack of grassroots support but Mr Blair's determination that there will not be a vacancy for many years to come.
Mr Brown publicly supported Mr Blair on his handling of key international issues - Iraq, the Middle East, climate change and global environmental damage - while conspicuously spending little time on the specifics of domestic proposals for foundation hospitals and variable university tuition fees on which trades unions are hoping to defeat the platform tomorrow.
And the Chancellor made an unashamed pitch for the party's "soul" in a speech containing more than 50 references to "Labour" rather than "New Labour" values.
In a play on Mr Blair's declaration last year that Labour was best when at its boldest, Mr Brown declared Labour was "best when we are Labour."
And in a variation of Mr Blair's vision of Britain as a "bridge" between Europe and America in international affairs, Mr Brown said Britain could be "a model, a beacon" for both, with its own values "marrying enterprise and fairness".
Pledging to make the case for the euro, provided sustainable convergence could be established, Mr Brown said: "Where America is enterprising but not today seen as fair, the rest of Europe more socially cohesive but not today seen as enterprising, Britain can become the first country of this era to combine enterprise and strength with a strong public realm."
Despite deepening doubts about his economic growth forecasts - and the implications for existing spending commitments and tax levels - Mr Brown promised conference that his next spending round would not only lock-in current levels of "investment" but also contain additional resources for front-line public services.
In a speech of towering ambition dedicated to "enterprise, opportunity and social justice" for all, Mr Brown again committed himself to the abolition of child and pensioner poverty in Britain, as well it seemed as to the provision of free healthcare for the children of the Third World.
He said it had been right to raise tax to increase investment in health and declared the case for a free National Health Service "stronger now" than when it was created in 1948. And he dismissed suggestions that the parties were now all the same and that there were no causes for which to struggle.
"I believe that at every point in our history, Labour needs not just a programme but a soul," declared Mr Brown. "Have confidence in our principles. Have confidence that these principles can be advanced in Labour policies for our time."
And, in that play on Mr Blair's conference speech a year ago, he continued: "This Labour Party - best when we are boldest, best when we are united, best when we are Labour." Invoking his economic muse of "Prudence", Mr Brown told the conference he would never ask them to abandon fiscal responsibility, or long-term reform for the quick fix. But if the road to change was sometimes "hard", Mr Brown urged his colleagues: "Then take inspiration from the unyielding determination of our pioneers; tough times did not diminish their idealism but made them even more determined that to transform lives you have to transform society."