John McCain pulled ahead of Barack Obama for the first time today in several key battleground states and in a fresh national poll, posing a central question for Democratic strategists: why is this 71-year-old Republican in such a “change” election year doing so well?

After gracing the covers of dozens of magazines and drawing record crowds and media attention for more than 18 months Mr Obama has found himself suddenly in a close presidential race against a man who has been on Capitol Hill for a quarter of a century, has suffered four bouts of skin cancer and who was a staunch supporter of the now unpopular war in Iraq.

In the past month Mr McCain has wiped out what had been a roughly eight-point lead enjoyed by Mr Obama nationally, and yesterday he was placed five points ahead in a Reuters/Zogby survey.

He has also pulled ahead slightly in several critical swing states including Florida, Missouri and Michigan. In Ohio, which is shaping up as perhaps the pivotal battleground, the latest poll had the Republican leading by 5 per cent.

There are fundamental reasons for the current success of Mr McCain, although there are still two and half months until the November 4 election and much can change.

The signature events of the general election campaign — the nominating conventions and the three presidential debates — have not taken place and Mr Obama could still pull away in the later stages. Yet Mr McCain is exploiting his vulnerabilities to great effect and genuinely believes that he will win.

The first factor in his success is that despite the unpopularity of President Bush and the Republican party, an electoral wipe-out akin to 1984 or 1972 is unlikely. Most analysts believe the race will be decided by no more than a few percentage points.

In July Mr McCain revamped his campaign team and put Steve Schmidt, the architect of President Bush's relentless “flip-flop” campaign that so damaged John Kerry in 2004, in charge of daily strategy.

He stopped the Arizona senator's freewheeling, and sometimes error-strewn, sessions with the press. The message was sharpened, the Bush model was adopted and they went to work on Mr Obama.

For the past month Mr McCain has released a barrage of negative advertisements against his young rival, painting him as feckless, obsessed by celebrity and too inexperienced to lead.

They stated erroneously that Mr Obama would raise taxes for working families. The commercials hit at the core of voter concerns about Mr Obama. Polls suggested that many more related to the values and background of Mr McCain.

Tad Devine, a Democratic strategist unaffiliated to the Obama campaign, said that his long primary battle against Hillary Clinton only “scratched the surface” of what people knew about him. Polls showed that many voters were worried about his youth and found his slightly exotic background — biracial, raised in Hawaii and Indonesia, and Harvard educated — as unnerving.

Mr McCain, despite being the oldest presidential candidate yet, “is immediately a credible candidate for president”, Mr Devine said, while Mr Obama is still “brand new to America, effectively unknown to the swing voters who are going to decide the election”.

Recent events have also helped Mr McCain. Mr Obama took a holiday in Hawaii for a week, ceding the stage to his rival. Russian tanks rolled into Georgia, a country the Republican has visited several times, reinforcing his message that only he has the experience to be Commander-in-Chief.

His hardline stance against Moscow resonated more with voters than the initially more even-handed approach of Mr Obama.

Mr McCain has also been successful in rallying his party's base behind him, in contrast to Mr Obama. A quarter of supporters of Mrs Clinton said that they would either vote for Mr McCain or are undecided, presenting him with a dilemma in advance of his nominating convention in Denver next week.

Then there is Mr McCain himself. He has enormous energy. He is funny. He came back from a near-terminal collapse of his campaign last year to win the Republican nomination.

His years as a Vietnamese prisoner of war make him a war hero. Perhaps most importantly, despite compromises and panderings to many constituencies in recent years, he has cultivated the image of a political independent.

Times Recommends

• Please help: maimed children of war want their lives back
• Cabal seizes diamond riches to buy power
• White House gatecrashers got to the president