Ignited by adversity, John McCain reached into his gut at a roof-raising rally in Pennsylvania yesterday to reveal a campaigner unwilling to be bowed by the headwinds of bad poll numbers and whispers of disunity in his camp, appealing to his supporters instead to "stand up, stand up, stand up and fight".

One week before the election, Mr McCain hit new levels of oratory as he and his running mate, Sarah Palin, rolled into Hershey, the chocolate capital of America, to tell his backers that the race for the White House was not over yet. It was a rally that began with them entering an ice hockey arena here on their bus, the Straight Talk Express, and ending with a McCain peroration as urgent as lightning.

It was an appeal to Republicans not to lose heart. Even after he acknowledged that pundits had "written off" his chances, Mr McCain, winding up the house almost without taking a breath, concluded: "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."

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It was the speech of a warrior-politician sensing he was perhaps making his last stand. The courage of his candidacy and of his campaign, that by any measure remains in dire straits, was reflected even by the map. That the McCain-Palin ticket is even competing in Pennsylvania, a state that has not voted Republican in a presidential race since 1988, was possibly plucky, possibly just reckless.

Or the campaign is facing up to difficult reality. Most polls still put Barack Obama ahead of Mr McCain by 10 or 11 points in the Keystone State. But if there is even the slightest chance Mr McCain can erase that lead, it is worth taking, not least because winning Pennsylvania means taking 21 electoral college votes on election night. That would offset losing some normally Republican western states to Mr Obama.

Mr Obama, moreover, is not so confident of holding Pennsylvania that he is ignoring the McCain-Palin onslaught. Just as the Hershey rally was starting, before a crowd of about 5,000, Mr Obama was in Chester, just outside Philadelphia, warning supporters in the pouring rain to guard against complacency. "We can't afford to slow down, sit back, or let up for one day, one minute, or one second in this last week," he said. "Not now. Not when so much is at sake." From Pennsylvania, he headed to Virginia, North Carolina and Florida, all toss-up states where he holds slight leads.

There was a brief kerfuffle in Hershey when a group of about six Obama supporters repeatedly tried to interrupt Mrs Palin as she made her opening remarks. After they were escorted out by security to raucous boos from the rest of the crowd, the Governor of Alaska suggested they should have been allowed to stay to "learn a thing or two from all of you".

Mr McCain is also battling to quash the Chinese whispers about schisms in his team, particularly growing divisions between his people and Mrs Palin's people. A writer with the website politico.com yesterday quoted a "senior" McCain adviser calling Mrs Palin a "whack job", which roughly translates as worryingly off her trolley. Two days ago she was described by another McCain loyalist as a "diva".

On the stage, Mrs Palin did nothing but play her part as the energising number two to her boss with all the gusto that has made millions of Americans either fall in love with her or run screaming. (Four young men on the terraces here filed out early from the rally after being heard to complain loudly that Ms Palin was not wearing a skirt as they had been hoping.)

As at every rally, the governor held up Joe the Plumber, first discovered by Mr Obama in Ohio two weeks ago, as the living symbol of all that is wrong with their opponent's tax plans. And she also had time to give a nod to the woman holding the sign, "Joe the Chocolate Maker".

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The Republicans have not been diverted by details of Joe the Plumber's resumé that suggest he would benefit more from the Obama tax platform than theirs. They instead see an opening to highlight adjustments the Democrats have made to their tax blueprint, particularly as to who would be hit by higher rates. "It's interesting how their definition of rich has a way of creeping down," said Mr McCain.

There may not be enough time for it to make any difference, but Mr McCain is determined, above all, to exploit Mr Obama's promise, made first to Ohio Joe, to "redistribute wealth". "Senator Obama is running to be Redistributionist in Chief," he said to applause. "I'm running to be Commander in Chief. Senator Obama is running to spread the wealth. I'm running to create more wealth. Senator Obama is running to punish the successful. I'm running to make everyone successful."

But the presence of both Republicans here was a reminder of the awful maths confronting them. Pennsylvania is now the only normally blue state still being contested. To have any realistic chance of winning next Tuesday night, Mr McCain has to capture three out of four eastern states – Pennsylvania, Ohio, Florida and Virginia. For now, Mr Obama leads in all them. On the other hand, most pundits calculate that if Mr McCain does not pull off a win in Pennsylvania, he will have to win all eight of the other states that voted for George Bush in 2004 that Mr Obama is mostly winning in for now.

In Hershey, Mr McCain may have found his sweet spot in Pennsylvania. Its chocolate factories aside, the biggest employer is the Hershey amusement park, about as conservative a place as you will find anywhere in America. Interviews with all the staff working in the Hershey Pantry on Chocolate Avenue hinted at some possibly encouraging news for the McCain team. At least two of the waiting staff, Brooke Shaffer and Summer Hawthorne, were categorically in favour of him over Mr Obama. The Democrat, Ms Shaffer, "is a bit cocky and that is definitely a turn-off for me".

And in the pantry there was at least anecdotal evidence, provided by 59-year-old Loretta Arndt, a secretary at a nearby military base, that fears raised about racism in Pennsylvania depressing the vote for Mr Obama may not be misplaced. "In the military you can't have anything against the blacks, you know, but I just don't think people are ready for that," she offers. "And this is Pennsylvania. People say they are going to vote for him, but when they get in the polling booth they are going to change their minds."

Pennsylvania: The Keystone State

* Pennsylvania in north-eastern America, with a population of about 12.4 million, has 21 electoral college votes.

* The last Republican president to be chosen by voters in the state was George Bush Snr in 1988.

* Won narrowly by John Kerry in 2004, it is the only Democratic-leaning state in which both Barack Obama and John McCain have campaigned before election day.

* With roughly the same political, ethnic and religious mixes as the rest of America, it is often seen as a microcosm of the country as a whole.

* Known as the Keystone State, it is one of the original 13 states that made up the United States. It was originally granted to William Penn by Charles II as payment for a debt owed to his family.