In a spirit of unyielding optimism neatly combined with a message of hard-headed pragmatism, Barack Obama has insisted that the time for American and European leadership "is now" in spite of the rise of new global superpowers. He was the first United States president to address MPs and peers in Westminster Hall and received a standing ovation before he began his speech, which covered issues such as foreign policy, economic development and international security.
The theatre of a state visit from Mr Obama is unavoidably mesmerising. Even the long wait in Westminster Hall for his arrival had a compelling quality, as Tony Blair spoke animatedly with Gordon Brown, David Cameron exchanged what seemed like a joke or two with Nick Clegg and opposite them sat the film star Tom Hanks. The delay in the presidential arrival led to an even greater sense of anticipation. Abroad at least, Mr Obama still casts spells as he did before the hard grind of power took hold.
The spell could not entirely obscure the limits of the message in his partly platitudinous speech and the awkward, plodding press conference that preceded it. Arguably, the platitudes were unavoidable. These are not occasions for provocative assertion, but for binding messages, ones that reassure and inspire disparate figures in the audience and well beyond. It would have been easy to insert the question "How?" after several of Mr Obama's proclamations on the need to spread freedom as part of an epic Churchillian defiance. The means are for another time.
Still, he made two substantial key points. In relation to foreign policy, he shares the Blairite view that people across the world yearn for democracy, but added an important qualification: that democracy cannot be imposed from outside. On this, David Cameron is in theoretical agreement and made the same point at their news conference. Both leaders euphemistically point out that they have learnt the lessons of history. They meant the recent lessons of Iraq.
But on the economy and the global financial crisis there was a stark difference. In spite of premature briefings in advance from the British Treasury that Mr Obama would endorse the Government's stark approach to deficit reduction, he did not do so. Instead, he praised the initiatives of governments to "yank" the global economy out of recession in 2008, a fiscal stimulus opposed here by Mr Cameron and George Osborne, and noted diplomatically that now countries were taking different paths in tackling the deficit.
Such occasions offer limited insight as to what will follow. After the seemingly crusading certainties of the publicly inarticulate George Bush and the silver-tongued Mr Blair, we have what appears to be the more nuanced approach of Mr Obama and Mr Cameron to military intervention.
There are some causes for optimism based on the pasts of the current leaders. Mr Obama opposed the war in Iraq in advance. Mr Cameron was astute enough to have a few private doubts about the war, but he voted in favour.
Both men seem, or seemed, to be more aware of the tumultuous consequences arising from military intervention.
At times, Mr Obama has been a reluctant warrior, pausing before taking action in Libya in contrast with Mr Bush, who wanted to invade Afghanistan with such speed that even Mr Blair urged a degree of patience. As a Conservative Prime Minister and after Iraq, Mr Cameron is under less pressure to prove he is a willing military ally to the US.
In particular, Mr Blair sensed he had to prove to Middle England and its newspapers that he would be an unswerving ally to a Republican president. From this expedient perspective he formed a convenient, but genuine, conviction that Mr Bush's instincts were correct. There is an assumption in the UK that a Conservative prime minister will be a reliable ally to the US anyway. Mr Cameron has nothing to prove in that respect.
But there is an echo. For Mr Cameron, Mr Obama is the mirror image to Mr Bush. While Mr Blair needed to show that he could forge ties with a right-wing Republican, Mr Cameron benefits from the gold dust of association with the superstar from the centre-left.
Now that Nick Clegg claims the progressives' mantle within the Coalition, the images of Mr Cameron playing table tennis with Mr Obama is something of a dream for the Tory leader. Mr Obama also will be thinking always of the second term, the defining election win.
Photographs of him at Buckingham Palace with the Queen might help to assure middle America.
This is a largely a ceremonial sequence. The real test comes with events. Although they agree about the dangers of imposing democracy from outside, their actions in Libya come close to doing so.
And there is a shared reliance on an economic recovery and a sense that only one of them can be right. Playing table tennis and serving hamburgers in a sunny Downing Street is the easy bit.
It is too early to judge whether Mr Obama and Mr Cameron will forge a more subtly effective partnership than Mr Bush and Mr Blair did.