I may be old but I'm good for two terms, McCain tells Republicans

John McCain has ended speculation that he might seek a one-term presidency, despite widespread concerns among voters about his age.

The Republican nominee, who turns 72 next week, would be the oldest first-term president in United States history but is resisting calls from campaign advisers who say that a single term in the White House might play well with voters in November.

"No," Mr McCain flatly told the influential website Politico.com. "I'm not considering it."

But in a damaging misstep, Mr McCain also declared that he does not know how many houses he and his wife own. The remarks were instantly seized upon by his opponent Barack Obama.

"Somebody asked John McCain, 'How many houses do you have?' And he said, 'I'm not sure, I'll have to check with my staff,'" the Illinois Senator said. "If you don't know how many houses you have, then it's not surprising that you might think the economy is fundamentally strong," he declared.

"But if you're like me, and you got one house, or you are like the millions of people who are struggling right now to keep up with their mortgage so they don't lose their home, then you might have a different perspective."

As the audience laughed the Democratic candidate added: "By the way, the answer is, John McCain has seven homes."

The gaffe is sure to haunt the McCain campaign in the weeks ahead as his opponent argues that the Republican candidate "doesn't get it" when it comes to the struggles of ordinary voters.

The latest NBC television/Wall Street Journal poll, on the eve of next week's Democratic convention in Denver, shows Mr McCain in a statistical dead-heat with his Democrat rival, but it also reveals deep public concern about his age. Nearly four out of 10 people asked said that Mr McCain is already too old to take on what must the most challenging job in the world. Some of Mr McCain's allies believe that declaring himself a one-term candidate would support his campaign message of putting the country first and silence a drumbeat of questions about his age.

If elected, at the age of 72, he would be too old to fly a commercial jet or even be a judge in some states. Despite ruling out a single-term presidency, Mr McCain's age is expected to be a major factor in his choice of a vice-presidential running-mate.

Some say his age heightens the importance of choosing someone that voters would be comfortable with should he die or become incapacitated while in office. Eight vice-presidents have succeeded presidents in this manner.

The Arizona Senator also promised that, if elected, he will run a more transparent and consensus-oriented administration than George Bush, offering to appear "once every couple weeks" before a British parliamentary-style "question time" for both houses of Congress. In theory, such an innovation would turn American politics on its head and underscore the Senator's strength as a gifted communicator.

Almost uniquely among American politicians, he has a talent for thinking on his feet and a quick sense of humour, although his off-colour jokes tend to backfire. He is also prone to displays of impatience and bad temper, raising doubts about his ability to remain cool under pressure.

Mr McCain has all but closed the gap with Mr Obama and leads him in a Reuters/Zogby poll, underscoring the apparent unease among voters about the country having its first black presidential candidate.

The NBC/WSJ poll showed the candidates neck-and-neck, with 42 per cent backing Mr McCain and 45 per cent for Mr Obama, down from a six-point advantage a month ago. Mr McCain's campaign strategist, Steve Schmidt, said the polls also showed "how wrong the Washington conventional wisdom has been on this race". The survey also revealed that the Obama campaign is still in trouble with voters who backed Hillary Clinton in the primaries. Only half now say they will vote for Mr Obama. One in five plan to vote for Mr McCain. These should be natural Obama supporters – they dislike Mr Bush, are ideologically liberal and tend to be women with incomes below $50,000 (£25,000). But they maintain that they see him as "arrogant and cocky".

In his Politico interview, Mr McCain promised regularly to offer "a full and complete explanation of what I'm doing and why I'm doing it", he said, adding: "I'm not being elected dictator – I'm being elected president."

As the media prepares to descend on Denver for a week of Democratic razzmatazz, the McCain campaign is doing what it can to steal Mr Obama's thunder. A few weeks ago, he unleashed a barrage of advertisements comparing Mr Obama to has-been celebrities Britney Spears and Paris Hilton. Much derided at the time, the ads appear to have worked, as the polls show.

* John McCain's Denver campaign headquarters was evacuated last night after an envelope containing a threatening letter and an unidentified white powder was received. Mr McCain was in Arizona.

America's oldest presidents

Ronald Reagan

In 69 (January 1981), Out 77 (January 1989)

As both the oldest ever elected president and the longest-living – he died aged 93 – Ronald Reagan would be John McCain's biggest age rival should he make it to the White House. Reagan made the move to politics late in life, having concentrated on an acting career during which he appeared in more than 50 films. Less than three months after taking office, Reagan survived an assassination attempt. Although wounded, his rapid recovery boosted his popularity and helped get him a second term with an unprecedented number of electoral votes. He presided over the longest period of peacetime prosperity the US has ever seen.

William Henry Harrison

In 68 (March 1841); Out 68 (April 1841)

Little did William Henry Harrison know that when he made his inaugural speech lasting an hour and 45 minutes that it would not only make him a recordbreaker – for the longest ever debut delivery – but that it would also lead him to develop pneumonia that would kill him just a month later. This wasn't his only entry in the American presidential history books – he was also the only leader to have studied as a doctor. His military service in wars against Native Americans earned him the nickname "Old Tippecanoe" after the Battle of Tippecanoe in 1811 and made him a national hero, popularity which swept him to power despite his advanced years.

James Buchanan

In 65 (March 1857); Out 69 (March 1861)

"My dear sir, if you are as happy entering the White House as I on leaving, you are a happy man indeed," wrote Democrat James Buchannan to his Republican rival, Abraham Lincoln, who succeeded him in 1861. He was glad to see the end of his single term as president, and with good reason. Historians voted his failure to avert civil war as the worst presidential blunder ever. Unlike John McCain, Buchanan promised in his inaugural address never to run again. He was the first president to publish a memoir, but his was a solitary life – he was the only leader of the free world not to have a first lady by his side.

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