It's a cold wet night in the countryside outside Philadelphia, rolling hills dotted with pleasant suburbs and occasional blasted small towns, boarded-up buildings and liquor stores where the proprietor stays safe behind bullet-proof glass.

Hillary Clinton is in a vast building big enough to assemble 747s. It's been built on a site long abandoned by US Steel and the growth of a new industrial centre here, it's meant to symbolise regeneration even after the big corporations have abandoned their workers.

The audience is mostly blue-collar-working class in coats and jackets turned up against the cold. By contrast she is in a powder-blue trouser suit, the subject of much mirth to the late-night comics. It's the kind of garment that makes horrified children say: "Mom, you're not going to the school play dressed like that?"

But she's always attracted that kind of bad-mouthing. "Why does Hillary always look as if she's telling you off for not cleaning round the bath?"

But this audience loves her - or at least the claque who are there to wave banners and cheer, love her very much. I noticed a steady dribble of people leaving in mid-speech, but in a hall that's almost too vast to see across, it's not easy to see who's leaving and who's heading for the toilets.

The cheers seem to give her a jolt of life - the audacity of hope, as her main opponent puts it - and even across the concrete acres you can see the eyes and teeth gleam with enthusiasm. She is ahead in Pennsylvania, a state she absolutely must win handsomely if she is to stay in the contest. Plenty of Democrats think she is behaving selfishly by staying in at all. Obama is now the likely winner and John McCain, the Republican, is happily watching the two Democrats kick lumps out of each other. As one New York Times commentator put it, some Democrats would love to slip a burlap sack over Hillary's head, and bundle her out of sight before anyone notices.

But even if she is tired, tearful and depressed she can't admit it, even to herself, not for one moment. She walks into the thump of Eye of the Tiger, the Rocky theme, a film about a white boxer who defeats among others a big tough black guy. Was it subliminal? I doubt it. In modern politics, glaringly obvious is the new subliminal, and today she made the point directly comparing herself improbably to the Sylvester Stallone character.

She said that ending her campaign now would be as if, "Rocky Balboa had gotten halfway up those art museum steps and said 'Well, I guess that's about far enough."'

"Let me tell you something, when it comes to finishing a fight, Rocky and I have a lot in common. I never quit. I never give up. And neither do the American people."

The claque cheers maniacally, and since then I've seen the clip a dozen times on TV. Watching television during an American election is like being trapped on a train by a bore, who insists on making the same point, in your face, over and over again.

The election has turned mean. Hillary's husband, who has spent the last seven or so years as a wise, far-sighted elder statesman, seems determined to re-invent himself on his wife's behalf as a bad-tempered dog. "I think it would be great if we had two candidates who love this country," a reference to Obama's former pastor, who famously led his flock in a rousing chorus of God Damn America. Saying too Obama doesn't love his country is the equivalent of saying: "It would be great if we had two candidates who aren't paedophiles?" It's way below the belt, as are some of Hillary's lines in the aircraft hanger - for example she implies that Obama would bring in universal healthcare except for people who need it, the old, the poor and sick.

She voted for the Iraq War and Obama didn't, so she now has to re-appear as a peacenik but a militant peacenik - "I think we need a commander in chief who not only respects our armed forces but provides them with the body armour and equipment they need." The implication that Obama would leave them to face the warlords dressed in pyjamas and driving golf buggies is left hanging in the air.

Hillary's biggest problem lately has been the time last week that she "mis-spoke", describing how, as first lady, she landed in Bosnia under heavy sniper fire when TV footage shows her strolling across the tarmac and being serenaded by a little girl. Cartoonists have had a wonderful time. "Then I gnawed through the ropes, knocked a couple of alligators out cold and pulled myself to safety ..."

"The new Indiana Jones movie?"

"No, just Hillary's stump speech," is typical.

(In fact other people on the trip have said there were real fears of sniper fire, and the party wore flak jackets. In which case, why did she take her daughter Chelsea along?)

Was the tale another Clinton lie? Can either of them ever present a fact without embroidering it, or making it up out of nothing?

Or was it the notorious sleep deprivation, either in the plane in 1996 or on the campaign trail? Either way, it makes nonsense of her campaign ad, the one that has the phone ringing at 3am and voters are asked who they would rather answer it - the implication being, not that inexperienced whipper-snapper.

Either way the mistake seems to have done great harm and has helped wipe out the memory of Obama's ferocious preacher. Some polls have him 14 points ahead among Democratic voters nationally.

But here in Pennsylvania she is playing the union card and playing it well. The language is all tied to them. "Who would you hire to do this job?" she asks. She keeps repeating the word hire as if the president was just another working guy with a lunch pail worried about his healthcare.

This morning speaking to a hugely sympathetic crowd she said: "I'll fight for you and I will fight for you as president." The militant peacenik even spoke lovingly of target-guided missiles because they are made in America. She came close to tears when she talked about a pregnant woman in Ohio who lost her baby and then died because she couldn't afford a hospital's $100 fees.

"A Clinton had to clean up after the last George Bush, and a Clinton's gonna have to do it again," she said.

Which is, after all the whole point of her campaign.