John McCain has embarked on a week-long biographical tour of America, re-introducing himself to voters by describing how a “martial heritage” had taught him the values of “honour, courage, duty, perseverance and leadership”.

The Republican presidential nominee-elect said today that he was an “imperfect servant of my country” — but one born into a family of rough-hewn American military heroes and redoubtable women who “made me the man I am”.

His soft-focus speech in Meridian, Mississippi, this morning made no mention of the Democratic candidates, Hillary Clinton or Barack Obama. Nor did he speak of current political issues such as the Iraq war or the faltering US economy.

Addressing a rally near McCain airfield named after his grandfather — an admiral — and where he had himself been stationed as a flight instructor, the 71-year-old Senator instead used his life story to explore broad questions about parental responsibility or the role of government in society.

Mr McCain talked of his rebellious youth and how he had failed to understand his family “until later in life when I needed it most” - an oblique reference to his imprisonment and torture during the Vietnam war. “They showed me how to love my country," he said, “and that has made all the difference for me, my friends, all the difference in the world.

The “Service to America” tour includes a trip tomorrow to his high school in Virginia where his open disregard for rules earned him the title of “worst rat”. On Wednesday he will stop at the Naval Academy in Annapolis at which he graduated fifth from the bottom of his class. Later this week he will visit Pensacola, Florida, where he attended flight school, drove a sports car and spent most of his free hours in bars or beach parties.

But his journey will also take him to Jacksonville where his first wife and young children lived while he was a prisoner of war, as well to Memphis for a speech marking the 40th anniversary of the assassination of Martin Luther King — which occurred when he was still incarcerated in Vietnam — and Arizona, the state he has represented in the Senate since 1986.

Although one observer pointed out today that in past four presidential elections voters have rejected military veteran candidates in favour of those with “lesser résumés”, Mr McCain now has seven months to build a campaign as "the American president Americans have been waiting for".

His Democratic rivals do not have such a luxury. Polling evidence suggests that the attacks on each other by Mrs Clinton and Mr Obama have damaged their prospects for November's general election — with Mr McCain holding his own against either of them.

Both Democrats campaigned in Pennsylvania this morning, which holds a potentially pivotal primary later this month. Mr Obama is on a bus tour on which he has been portrayed him in a variety of “regular guy" poses, drinking beer in a bar, playing basketball or attempting — with limited success — ten-pin bowling. Mrs Clinton is concentrating on harder-edged speeches about the economy.

The Obama camp played down reports this morning that a steady trickle of super-delegate endorsements was set to become a flood, while Bill Clinton said that Democrats urging his wife to quit the race should just "chill out".

The former vice-president Al Gore was today similarly dismissive of speculation that he would be the “honest broker” who would halt the fight. He compared any such figure to a “modern Boss Tweed” — a reference to the corrupt 19th Century politician who ruled over the Tammany Hall Democratic machine in New York.

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