After a two-year White House odyssey in which he has veered between comeback kid, warrior politician, courageous independent, steady leader, attack dog and maverick rebel, a roaring crowd in Pennsylvania finally looked on this week to something approaching the real John McCain.

“I'm an American,” Mr McCain yelled, pounding the podium. “And I choose to fight. Don't give up hope. Be strong. Have courage ... Fight for a new direction for our country. Fight for what's right for America!” Ending a speech in which he had - at last - found a consistent message, one that decried Barack Obama's agenda, cut his ties to President Bush and connected to the middle class, the Republican brought his flag-waving audience to their feet.

“Stand up, stand up, stand up and fight! America is worth fighting for. Nothing is inevitable here. We never give up. We never quit. We never hide from history. We make history. Now, let's go win this election and get this country moving again!” It was a powerful performance, and authentic, reminiscent of the John McCain that burst on to the national stage in the 2000 Republican primary when his free-spirited “Straight Talk” insurgency - for a heady moment - threatened to topple George W. Bush's presidential juggernaut.

For John Sidney McCain III, 72, this is his last shot at the presidency, after a campaign in which he has already pulled off one of the most mesmerising political comebacks of modern times in the Republican primary this year, having been written off as dead months earlier.

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The former naval fighter pilot and Vietnamese prisoner of war, a man imprisoned and tortured for five-and-a-half years in the notorious Hanoi Hilton, still believes he can defeat Barack Obama next week. Polls yesterday suggested that the race is tightening significantly in a number of battleground states and his aides rightly insist that he still has a route to victory.

Yet if he does pull it off, it will be after a campaign in which too often his opponent was not only Barack Obama but John McCain himself. For months, as the Arizona senator has veered from tactic to tactic, from a genuine desire to run a noble campaign to attempts to link his rival to a former domestic terrorist, he has suffered an internal struggle between his better angels and an all-consuming thirst for victory.

Mr McCain, whose father and grandfather were navy admirals, and who refused offers of early release by his Vietnamese captors, entered this White House race exhibiting a bewildering and often alluring mix of contradictions. He has a mind and body that has suffered far more wear and tear than most but still has frenetic energy.

He is pugnacious, impatient, courageous, at times quite menacing, charming, has an unmistakable mean streak, is often irreverent and fiercely patriotic. He is a man of strong views forcefully expressed, and frequently takes principled stands - most recently over his support for the Iraq surge and immigration reform - that he knew could damage him politically. Indeed, his call to allow illegal immigrants the chance of citizenship was one of the major factors in the collapse of his primary campaign last summer. Yet he is also capable of craven compromise.

But in recent months, he has come dangerously close to losing what once made him so special and so attractive to swing voters: his image as a political independent happy to buck party orthodoxy. It was a brand that perhaps made him the only Republican capable of winning the White House in a year when the political winds are blowing at gale force behind Democratic backs.

Mr McCain was on his 23rd bombing mission on October 26, 1967, when his aircraft was hit by a surface-to-air missile over Hanoi, North Vietnam. He ejected, was knocked unconscious and broke both arms and his right knee. Captured, he had his shoulder broken by a rifle butt and was bayoneted in the ankle and groin. His captors never reset his arms.

The Vietcong, determined to extract a confession, lashed his arms behind his back, tightening the rope throughout the night. Eventually, he confessed to “deeds of an air pirate”, a statement that still haunts him. In captivity, he attempted suicide.

Mr McCain talks animatedly about the ideals of service to one's country, and of having the courage to do what is right. Yet in recent months, he appears to have become less his own man.

He began his campaign against Mr Obama as the candidate of experience. Then, reluctantly, he agreed to trumpet his captivity in Vietnam, to project an image of a courageous warrior. In the summer, lagging behind Mr Obama, Steve Schmidt, a veteran of President Bush's 2004 re-election campaign, took over day-to-day operations. Mr McCain was muzzled. Gone, overnight, were freewheeling sessions with journalists. Press conferences were stopped. He was ordered to stick relentlessly to the “message”.

Yet the message has changed constantly. So too has Mr McCain's attitude to attacking Mr Obama's past associations. One week he would lambast him for his (tenuous) ties to William Ayers, the former domestic bomber. Then he would pull back from the fray. His most noble decision has been a refusal, against pleas from aides, to bring Mr Obama's controversial former pastor, Jeremiah Wright, into the mix - the one figure from the Democrat's past that had the potential to derail his campaign.

In September he temporarily suspended his campaign to return to Washington when the financial crisis hit and called on Mr Obama to postpone their debate. It was a stunt meant to show leadership. It backfired, leading many to wonder if Mr McCain could ever be anything but an impetuous seat-of-the-pants fighter pilot.

He wanted Joe Lieberman, Al Gore's 2000 running-mate, to be his vice-presidential pick. He was told it would alienate the Republican base. So he went with Sarah Palin. Overnight, the message changed again, from experienced leader to maverick.

In recent days, however, Mr McCain has found his voice, especially in sowing doubts about Mr Obama's plans to raise taxes on people earning more than $250,000 annually.

“We're closing in, my friends,” he declared yesterday in Ohio. He just hopes that it has not come too late.

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