Don't stretch your credibility, Mr Obama

Here was the most minutely choreographed convention on record: from the vast Doric columns framing the stage (presidential, moi?) to the lavish colour co-ordination and carbon-splurging fireworks of the final hurrah.

It was the no-holding-back moment for a man who has sealed his deal with his own party and now needs to woo the key undecided 15-20 per cent of voters who will decide whether he makes history as the first black President - or goes down as the greatest Democratic disappointment in a century.

"This is not about me," said Mr Obama though naturally most of it was. No politician on the world stage is so skilled at weaving stories of his family history into a purposeful narrativesoliciting agreement - from his mother's fight with the insurance companies when dying of cancer to his grandfather's lucky chance at education as a returning veteran.

Readiness was the theme - readiness to lead and a feisty fightback on his weakest flank: his inexperience for a man contending to be commander-in-chief.

But what will shape the campaign of the next weeks were the spending commitments - a tax cut for working families and a promise to end US dependence on Middle East oil in a decade.

As one Republican strategist remarked, that amounts to spending something above $200billion in the first 10 minutes of a speech.

Not that his audience was counting - their man could blow the entire GDP in one go and they would applaud it.

He has his party in the palm of his hand in a way we have not seen since the height of Bill Clinton's popularity.

It may have been a speech pitched rather too close to the hearts of Democrats for his broader good: the list of deliverables - health care plans, better education and a green revolution are so familiar that most Americans know they mean massive spending if taken seriously - all that with a tax cut on top.

Mr Obama will have to beware that his pledges do not stretch credibility in economically straitened times.

After a bruising campaign against Hillary Clinton, Mr Obama paid his debt briefly to her husband's legacy, contrasting the economic record of the Bush years with the heady days of the Clinton boom "when 23million new jobs were created". That was that.

Mr Obama has shown that he does not believe he stands in anyone's shadow.

Stability, security and judgment will be the attributes fought over when he locks horns with John McCain in the weeks ahead.

Last night he argued that his judgement in opposing the Iraq war has been better than Mr McCain's but the speech was thin on foreign policy and security for a man who, if elected, will inherit a divided Nato, bellicose Russia, difficult engagement from Iraq (he has wisely stopped promising instant withdrawal) and the need to refocus the Afghanistan mission.

He spoke critically of the Bush failure to "take out Osama bin Laden" but there is no guarantee a Democrat White House would have more luck.

The sole line on Iran, "tough, direct negotiation" to prevent it flouting nuclear agreements was a reminder of how easily he can slip into slightness on the harder-edged questions.

"We all put our country first," he said, reclaiming patriotism for the Democrats and reworking his best rhetorical coinage "not a red America, not a blue America, the United States of America" to embrace the armed forces.

Mr Obama polls weakly among families where his opposition to Iraq is read as disregard for the achievements of servicemen. He is on firmer ground with his vision of a kinder, safer America, pledging to "uphold the second amendment (on gun ownership) but keep AK-47s out of the hands of criminals".

Some lines should be left behind in the Democrat memorabilia. His variant on the biblical theme of promise "that brought workers to picket lines" will not resonate outside the pro-union faithful. But you only had to listen to Al Gore speaking before him to realise what a strong communicator Mr Obama is.

That remains his outstanding strength in the battle with Mr McCain, who has his own weaknesses of mood, stubbornness and speech delivery.

"If he wants a debate on who has the temperament and judgment to lead America, that's a debate I am ready to have," was Mr Obama's challenge.

That is what it will come down to, when the temple has been consigned to the recycling bin.