The ever-fiercer struggle for the Democratic nomination moved to battlefields new in North Carolina and Indiana yesterday – with a resurgent Hillary Clinton vowing she had a better chance of defeating the Republican John McCain, and Barack Obama insisting he was still on track for eventual victory.
Hours after what Mrs Clinton described as an "overwhelming" win in Pennsylvania, she served notice she was in the fight until the end of the primary season on 3 June, and if necessary beyond.
"We're going to go through the next nine contests and I hope to do well in many of them," she said. "I'm confident that when delegates – as well as voters, like the voters of Pennsylvania just did – ask themselves who's the stronger candidate against John McCain that I will be the nominee of the Democratic Party."
Her remarks, to NBC television, were an open acknowledgement that, in what remains for her a steeply uphill fight, she has to win over the uncommitted "superdelegates" without whom neither candidate can secure the 2,024 delegates needed to win at August's convention in Denver, Colorado.
As expected – and widely feared by the Democratic Party establishment – Tuesday's Pennsylvania primary only muddied further the increasingly nasty contest for the nomination. The prime beneficiary of the protracted struggle is now Mr McCain, able to focus statesman-like on the general election while his two potential competitors rip into each other.
With more than 99 per cent of the vote in, Mrs Clinton had won by 54.6 per cent to 45.4 per cent. But the 9 per cent margin was neither the squeaker win that would have allowed Mr Obama to claim a moral victory and generate new demands for her to throw in the towel, nor the sweeping double-digit triumph that might have turned the race on its head.
"The tide is turning," Mrs Clinton proclaimed in her victory speech in Philadelphia. But the vote barely shifted the all-important delegate count. According to the Associated Press, Mrs Clinton won at least 80 of the 158 delegates at stake while at least 66 of them went to Mr Obama, with 12 still to be awarded.
In the overall contest, the Illinois Senator leads by 1,715.5 delegates to 1,589.5. Though trailing in pledged delegates awarded in primaries and caucuses, Mrs Clinton as of yesterday was still ahead among the 796 superdelegates, by 258 to 232, with roughly 300 yet to declare a preference.
Of the remaining primaries, North Carolina – where Mr Obama is a strong favourite thanks to his support among black voters – is the biggest prize. But the most closely watched battle will be on 6 May in Indiana, a part-industrial, part-rural Midwestern state where the two candidates are running neck and neck, and where both were campaigning yesterday.
In the meantime, the indebted Clinton campaign's top priority is to shore up its finances. Going into Pennsylvania, the Obama campaign had $42m (£21m) cash in hand, five times that of its rival. The disparity enabled Mr Obama to outspend his rival more than two-to-one in organising vital television advertising in Pennsylvania.
But within hours of the result, Clinton managers announced that more than $3m of new money had flowed into the campaign. They hailed the burst of fundraising as proof of donors' confidence that their candidate could still win the nomination – despite Mr Obama's lead in states won, delegates awarded and share of the popular vote that she has next to no chance of overturning in the nine contests that remain.
Last night, the Obama camp was still confident of ultimate victory. Mr Obama told CNN radio that he had made "terrific progress" in Pennsylvania, while his campaign manager, David Plouffe, said the nine remaining contests, ending in South Dakota and Montana on 3 June, would not change the dynamic.
"We don't believe the structure of the race is going to change fundamentally," Mr Plouffe said. "We believe there is an enormous amount of data that shows we're the stronger candidate."
In fact, Pennsylvania merely underlined the split in the party's core constituencies that has been exposed by the protracted nomination battle. As elsewhere, older, poorer and white voters trended heavily towards Mrs Clinton, while Mr Obama enjoyed the overwhelming support of blacks, as well as of younger, more affluent and better-educated voters.
The fear of party elders is that, with scant policy difference between the pair on most issues, the battle will degenerate into a poisonous and personal slanging match, providing ammunition for Mr McCain in the autumn.
Mr Obama yesterday again promised that he would not go negative, saying that would only "erode my support". He also signalled his opposition to another debate with Mrs Clinton, after 21 candidates' debates thus far. His rival, however, is urging two more debates in the fortnight before Indiana and North Carolina go to the polls.