Perhaps the comparison was inevitable: weeks ago Hillary Clinton, on the ropes against Barack Obama, compared herself to Rocky Balboa, the gritty Philadelphia boxer who triumphed over the odds.

She recalled a famous scene when Rocky forced himself to run up the steps of the Philadelphia Museum of Art, saying that ending her presidential campaign before Pennsylvania voted would be as if "Rocky Balboa had gotten halfway up those art museum steps and said, 'Well, I guess that's about far enough'". Early forecasts predicted a margin of 10 per cent Last night, glowing in victory, she roared: “Some people counted me out and said to drop out, but the American people don’t quit and they deserve a president who doesn’t quit either!” It was her Rocky moment supreme. She won in Pennsylvania not with a well-crafted, classy fight plan but by relentless, often wayward punching, and by convincing voters she would fight for them in the White House. She also won because the audience didn’t cheer on sufficiently an opponent who they don’t know well and whose name they have trouble pronouncing. Speaking at a hotel ballroom just a few blocks from the Independence Hall, where the Declaration of Independence was signed in 1776, Mrs Clinton praised the people of Pennsylvania for exercising their democratic rights in her favour. But her only hope of victory lies in overturning the popular will expressed by voters during the primaries and caucuses with the support of the party’s “super-delegates”, who have a free vote at the party’s nominating convention in August. Mr Obama has an insurmountable lead in the numbers of pledged delegates chosen during the primaries and caucuses, so Mrs Clinton has no option but to twist the arms of 300 or so super-delegates who have yet to make up their mind that she would be more better able beat Republican John McCain. There were noisy celebrations in Philadelphia’s historic centre last night, with cruising cars beeping their horns and Hillary fans waving their banners in the streets. But winning by a super-delegate coup would be a victory that many Democrats would consider a low blow, and not worthy of Rocky at all. By Alex Spillius in Philadelphia