Hillary Clinton pulled off a thumping 10 percentage point victory over her rival Barack Obama in Pennsylvania.
The dramatic sweep of her victory last night threw a financial lifeline to her near bankrupt campaign and boosted her case for remaining in the race.
"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," Mrs Clinton told supporters jammed into a hotel ballroom. She was accompanied by Bill Clinton and her daughter Chelsea who played a large part in her victory, campaigning tirelessly across the state.
Mrs Clinton has now won another opportunity to persuade the Democratic high command that she is the tougher candidate, better prepared to defeat the Republican candidate John McCain in the general election in November.
The six-week campaign saw her excoriate Mr Obama – who still leads in the popular vote as well as the delegate count for the nominating convention in August – and portray him as an ineffectual elitist to the state's white working class voters.
The tactic worked for Mrs Clinton who captured vast swathes of rural and small town Pennsylvania, while Mr Obama won very heavily in the Philadelphia which has a large black population. Pennsylvania is viewed as an electoral microcosm of the US and Mrs Clinton will now attempt to persuade the 311 remaining uncommitted superdelegates, mostly senior party and elected officials, to come over to her side and secure the nomination.
But she faces huge obstacles ahead, not least the millions of dollars of debt her campaign has run up. Democratic party leaders also fear that the ferocity of the nomination fight could wreck their prospects of winning the White House in November. While Mr Obama outspent Mrs Clinton three to one in Pennsylvania he did not come close to challenging Mrs Clinton. But thanks to earlier victories in smaller states, Mr Obama still leads in the popular vote and he is so far ahead in the race to win the 2,025 delegates he needs to secure the nomination that she cannot catch him.
Mrs Clinton cut slightly into Mr Obama's delegate lead winning at least 66 delegates to the party's national convention (with 35 still to be awarded). Despite his defeat Mr Obama collected at least 57 delegates which are allocated by proportional representation.
In the overall race for the nomination, Mr Obama leads with 1,705.5 delegates, including superdelegates. Mrs Clinton had 1,575.5 delegates, according to he Associated Press tally.
Mrs Clinton's only possible path to victory is through the superdelegates. Recognising this she was gracious in her victory speech in Philadelphia last night. Rather than attack Mr Obama, she addressed the voters in the upcoming states of Indiana and Nor Carolina while painting a more human side of her personality.
Earlier yesterday she played up Americans fears of terrorism as well as worries about an Iranian nuclear attack on Israel to make the case that she would be a better commander in chief.
"I want the Iranians to know that if I'm the president, we will attack Iran," she She told ABS news . "In the next 10 years, during which they might foolishly consider launching an attack on Israel, we would be able to totally obliterate them."
The lesson she appears to have drawn from her victory is that negative works. In an editorial this morning, the New York Times, which is endorsing her run for the presidency said her campaign was worse that the "mean, vacuous, desperate, pander-filled contests that preceded it."
Mr Obama did not escape the newspaper's wrath either, but the focus of the paper's anger was on Mrs Clinton saying that her tactics do "nothing but harm to her, opponent, her party and the 2008 election."
The lesson Mrs Obama has drawn from the campaign is that he now needs to use his huge financial edge to try and crush her in Indiana and North Carolina which vote n two weeks time.
Mr Obama has a war chest of $42 million collected in March against $21 million Mrs Clinton raised and can vastly out spent her in political advertising.
In her victory Mrs Clinton was quick to ask her supporters to log onto her website and donate more money, telling them "We can only keep winning if we can keep competing with an opponent who continues to out spend us massively."
Amid the euphoria of her victory her officials claimed their best night ever in internet fund-raising which they said had brought in $2.5 million in a few hours.
The upcoming Indiana primary, is viewed as another key test for Mrs Clinton, who is slightly ahead in the polls there. But Mr Obama faces his own problems, thanks to the bitterness of his nomination battle with Mrs Clinton. As he goes into North Carolina any attempts by the Republican party or Mrs Clinton to highlight his association with his firebrand pastor Jeremiah Wright could be toxic for him.
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