Phil Sowell, a retired government official, scarcely pauses for breath when asked what Barack Obama would do as President: “He will bring peace to the Middle East and anywhere in the world where there is tragedy.”

But Larry Milton, 56, thinks that “he will be more worried about what happens here and less worried about other countries”. Carrie Thompson hopes that he will “address global poverty and other issues which Republicans keep overlooking”, while Ron Gaynor, 52, a lifelong Republican, says: “He will bring the power of veto and say ‘no’ to a lot of this government spending – we seem to give money to people all around the globe.”

They are all waiting to hear the man himself speak. It is a familiar scene, repeated across America dozens of times in recent weeks. Long queues snake around a sports hall – comprising people of all ages, races and social class – to gather under the Democrat presidential contender’s slogan of “change we can believe in”.

But what, exactly, is this change in which they all believe? The Times conducted more than 50 interviews at a rally in Westerville, Ohio, where many supporters made plain they have contradictory – and burgeoning – expectations of what “President Obama” would do.

Sarah Jaffy, 41, says: “I really like his healthcare plan. And there’s another policy – it’s my favourite – ooh, I can’t remember right now.” Erin Henderson, 18, has gone with a gaggle of friends to see Mr Obama and she declares: “We’re all really excited about him and we heard he might make it easier to get into college.”

Today these voters could tip the balance of the Democratic presidential race Mr Obama’s way. If Hillary Clinton loses Ohio and Texas, most observers – including her husband, Bill – say her candidacy will fail.

She has become increasingly frustrated at seeing her poll leads evaporate in the heat of Mr Obama’s phenomenal appeal. She rails against his soaring oratory, saying: “I could stand up here and say, ‘Let’s just get everybody together, let’s get unified.’ The sky will open, the light will come down, celestial choirs will be singing, and everyone will know that we should do the right thing and the world will be perfect.”

But Mr Obama’s coalition of voters suggests his message is succeeding in reaching out, not only across the racial divisions that have long scarred America, but also over the partisan political landscape that has characterised the Clinton-Bush era.

As such, he resembles another charismatic youthful politician who made ephemeral promises of hope, change and a new approach to government: Tony Blair in the UK 11 years ago.

It is a comparison not lost on Mr Obama’s admirers, who answer charges that support for him is a passing fad by pointing out that the former Prime Minister won successive landslide election victories before his star began to fade. And, while British is politics is often dragged down by cynicism, the optimistic American psyche that is always open to a promise of “new leadership” and a “new beginning” may keep Mr Obama afloat for longer.

Mr Blair, however, could offer evidence for his claim to stand for postpartisan politics, having defeated the old left of the Labour Party by dumping the Clause IV promise of mass nationalisation and steering the party towards the “radical centre” over three years in opposition.

Mr Obama, by contrast, can only really show a campaign that is winning support from many independent and Republican voters – despite having, according to a study by the National Journal, the most liberal voting record of any US Senator.

Mrs Clinton last week cited a passage from Mr Obama’s book, entitled The Audacity of Hope, “where he said that he is a blank screen and people of widely different views project what they want to hear”.

The full quote, however, is more interesting. Mr Obama said he had many orthodox opinions as a Democrat and a black man, before adding: “That is not all I am. I also think my party can be smug, detached and dogmatic.” He then set out views – on the free market, patriotism, spirituality, and a politics not based solely on “victimhood” – which he predicted will “get me into trouble”.

Although admitting that he was new enough to be a blank screen on which “people of vastly different political stripes project their own views”, Mr Obama added: “I am bound to disappoint some, if not all of them.”

But, perhaps, not quite yet. At Mr Obama’s Westerville rally, Eric Whitaker, a member of his coterie of friends travelling with him, discusses with passing British journalists any lessons to be learned from the Blair experience. “I guess the big challenge of leadership is disappointing your supporters at a rate they can deal with,” he says.

As he speaks, Senator Jay Rockefeller, a national security expert, is on the stage explaining why Mr Obama is qualified to be commander-in-chief. “It’s just how you feel about it,” he says. “I trust him.”

Sitting in the audience, Alex Dukeman, 17, says that she expects Mr Obama to introduce universal healthcare. But isn’t his plan voluntary while Mrs Clinton promises a compulsory mandate? “I just think he is a likable guy and he inspires people,” she replies. Zach Adriaenssens, 20, says that Mr Obama is a “unifier” who can negotiate with Republicans “and will sort healthcare”.

Donny Murray, 21, says that Mr Obama “has definitely got a better plan” for tackling global warming. How so? “I’m not sure about the specifics, I just think he’ll get more people involved,” he says. Freda Graan, 27, a Spanish teacher at Ohio State university, explains: “If you listen to Hillary, she says, ‘I will do this’. Obama says, ‘We will do this’. I’m not scared to be idealistic, it’s my responsibility as a voter not to be cynical.”

Yusuf Abdi, 55, says: “He will change everything – healthcare, no war, education. He can do anything.” Karen Clark, a teacher, 58, says that she has switched her support from Clinton because “I want to be on the winning side”.

When Mr Obama arrives on the platform, many in the crowd hold cameras above their heads to capture the moment, giving the appearance of a massed double-armed salute. As ever, a woman screams: “We love you Obama!” He replies, as usual, “I, uh, love you back.”

His speech is low-key, lacking some of his higher flights of rhetoric but heavy with policy specifics, possibly a sign of how sensitive he remains to Mrs Clinton’s recent criticism, which he spends a long time rebutting.

But his proposals are not “tough choices”, favoured by Mr Blair, but of a type that will not make him new enemies. Mr Obama, for instance, talks of a “middle-class tax cut” which will “make life more affordable for 95 per cent of Americans”.

Outside the hall is Robin Lease, 52, a lycra-clad teacher who has just jogged two miles from Mrs Clinton’s rally across town. “I wanted to see them both speak,” she says. “I would tend to vote for Obama – I think he would be more liberal on social programmes,” she says. “But then again, I’m a Republican. I know that sounds confusing.”

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