Hillary Clinton’s rally yesterday was brought to its feet with a blast of theme music from the Rocky movies — filmed in nearby Philadelphia — that tell the story of an underdog boxer battling against the odds and refusing to go down.

So it is with her campaign. Despite being bloodied in round after round of her bout with Barack Obama, Mrs Clinton keeps coming back off the ropes — more aggressive and determined than ever before.

In Harrisburg yesterday, in front of 1,700 people, she revelled in her new role. When her microphone failed, she fetched another. When she briefly had a coughing fit, a woman shouted: “You can do it, Hillary!” And she did.

She scorned the gap between Mr Obama’s “talk and action”, citing recent comments from his advisers, which cast doubt on his policies over trade and Iraq. “If you talk, you’d better mean what you say,” she declared.

Mississippi had been abandoned long before it voted yesterday. Instead, Mrs Clinton preferred to spend her time here in Pennsylvania, which hosts a primary in six weeks and — like Ohio and Texas last week — has become a must-win contest for her.

Pennsylvania, where the Battle of Gettysburg helped to settle the American Civil War, could help resolve the Democratic fight if she loses on April 22. Mr Obama is confident that he will remain on course for the nomination even if Mrs Clinton prevails here. “We’re not a believer in symbolic wins,” says the campaign manager, David Plouffe, who repeatedly refers to “the math” that shows that she cannot close a 100-plus elected delegate gap before the convention.

This has, however, become almost a badge of pride for Mrs Clinton’s campaign. She will not give up — and her stump speech these days is littered with references to hard-working, fighting qualities, which, as in Ohio, go down well with this electorate.

Some even describe Pennsylvania as “Penn-hio” because the demographic make-up is so similar to the scene of her victory last week. It suits her that this state is older, more working class than the rest of America — and whiter — with few black people to be seen at either her rally in Harrisburg or a later meeting in Philadelphia.

Mrs Clinton has the backing of the local political Establishment including the Governor, Ed Rendell, and Michael Nutter, the black Mayor of Philadelphia — who supports her even though the large African American population of his city and its prosperous liberal suburbs are seen as fertile ground from Mr Obama.

Another factor in her favour is the roots that her father’s family, the Rodhams, laid deep in this state. On Monday night she spoke in Scranton — a town chosen as the fictional location for the US version of the sitcom The Office — where she reminisced about summer holidays spent near by at her family’s Lake Winola cottage.

As Christopher Doherty, the Mayor of Scranton, put it: “She’s tough. That’s a real Scranton trait. That’s an anthracite trait.”

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