Under a setting sun, with the barges of the Mississippi passing lazily behind him, Barack Obama is shouting – his arms raised, leaning towards the crowd of Iowans with the urgency of a man who knows time is running out.

“I come from a new generation of Americans,” the 46-year-old booms. “I don’t want to fight the battles of the 1960s.”

The audience applauds with the first real passion of the night. Without mentioning her by name, they know whom he is referring to.

He turns to Iraq, a war Hillary Clinton voted to authorise in 2002. “I opposed this war in 2002, 2003, 2004, 2005 and 2006,” he continues. “The judgment that matters most is the judgment made first. Now is the time to be bold. Now is the time to turn the page on Iraq in a way to turn around our foreign policy!”

But with only four months until the crucial first Iowa caucuses, the opening votes in the contest to become the Democratic presidential candidate, Mr Obama knows that he has to turn around a campaign that has been stuck in neutral for months.

Despite the huge and enthusiastic crowds that Mr Obama continues to draw across America and his record-breaking fundraising feats, the Illinois senator has languished about 20 points behind Mrs Clinton in national Democratic polls since the spring.

The African American, blessed with charisma but dogged by accusations that he lacks the experience and foreign policy gravitas for the Oval Office, trails the former First Lady by 18 per cent in the first primary state of New Hampshire. He is well behind in South Carolina, another key early region that he had hoped to excel in because of its large black population.

But in Iowa, whose voters every four years become the first to deliver their often make-or-break verdicts on presidential contenders, Mr Obama is in a statistical tie with Mrs Clinton.

So this week, in this Midwest expanse, he launched a final, all-out political surge to close the gap on a rival who has run one of the most disciplined and effective primary campaigns of recent times, and who has so far succeeded in portraying him as a political neophyte unqualified to take on America’s enemies.

In case anybody might be in doubt over the target of Mr Obama’s new push, it began on Wednesday in a town called Clinton, Iowa. There he delivered a speech on Iraq: his prescription to end the war by pulling all combat troops out by the end of next year.

Then he took off across Iowa, holding a series of “town hall” meetings with voters in a state that has the second-highest percentage of people over 85, an ethnic minority population of only 6 per cent, but whose quadrennial first-in-the-nation voting status gives it enormous influence.

His aim, aides say, is simple. If Mr Obama can win the Hawkeye State the race could be transformed. His strategy is simple: to convince enough voters that after 16 years of partisanship and division, a Clinton restoration will only prolong the dysfunction crippling national politics; and that he has the judgment and foreign policy vision to take on America’s myriad challenges abroad.

Mrs Clinton, by contrast, has a new message of her own: only she can deliver change, because she has the pedigree to do so. “Change is just a word without the strength and experience to make it happen,” she said in a speech last week. “You bring change by working within the system. You can’t pretend the system doesn’t exist.”

In recent weeks Mr Obama has held dozens of foreign policy seminars with a formidable team of advisers who worked in the Bill Clinton White House but have not signed on with his wife.

They include Anthony Lake, Mr Clinton’s first-term National Security Adviser; Susan Rice, a protégé of Madeleine Albright, the former President’s Secretary of State, and Richard Clarke, a former chief counter-terrorism official in the Clinton and Bush White Houses. Mr Obama will soon deliver another “major” foreign policy address on US defence and military policy.

Towards the end of his appearance in Dubuque, Mr Obama is reaching out to his audience. He is away from the podium, microphone in hand, prowling and turning. “Too many politicians feared looking weak and failed to ask the hard questions,” he says, referring to Congress’s – and Mrs Clinton’s – backing of the Iraq invasion.

“I took a different view. I wouldn’t be running if I didn’t have the right experience to lead the country. I am here today because we are not too late to come together as Americans. It’s time for us to reclaim our foreign policy.”

As Mr Obama left the stage and worked the crowd on his way out to the strains of Aretha Franklin’s You Better Think, Dale Blesz, 47, who was undecided between him and Mrs Clinton before the speech, said: “He inspired me to support him.” Can you see him as President? “I really think so. He’s got the moral backbone. He’s far more real than Hillary.”

Diane Dardon, 51, said: “I can see him as President. He’s bold enough to fight for some new ideas.”

Strange things happen in Iowa. John Kerry resurrected his moribund primary campaign here in 2004. Mr Obama told the crowd that he would be coming back often.

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