Londontimes Barack Obama took a potentially decisive step towards the Democratic nomination today after scoring a big victory in North Carolina and forcing the Indiana election down to the wire.

Mr Obama's big win in the Tar Heel state robbed Mrs Clinton of the "game changing" victory she badly needed to alter the course of the Democratic nomination battle, while the closeness of the race in Indiana added to the sense that she is rapidly running out of time to wrench the nomination from her rival's grasp.

Mr Obama took a 14-point win in North Carolina and kept the scale of Mrs Clinton's victory in Indiana down to 2 per cent and little more than 20,000 votes, making it a deeply disappointing night for the former First Lady.

She will today face renewed pressure to drop out of the race. Mrs Clinton insisted that she would carry on, possibly all the way to the final contests in South Dakota and Montana on June 3. But in his victory speech in Raleigh, North Carolina, Mr Obama — while graciously praising his opponent — sounded like a nominee-elect.

He ended the night with an increased lead among pledged delegates and having erased Mrs Clinton's popular vote margin in Pennsylvania's primary on April 22. In his speech before a cheering crowd, Mr Obama predicted that the Republicans will attack him over his race.

He said that they will "label and name call" — a reference to recent controversies including the incendiary remarks of his former pastor — and declared: "I trust the American people's desire to no longer be defined by our differences."

He added: "That's why I'm in this race. I love this country too much to see it divided and distracted at this moment in history. I believe in our ability to perfect this union because it's the only reason I'm standing here today. And I know the promise of America because I have lived it." Referring to Mrs Clinton's recent prediction that North Carolina would dramatically alter the race, Mr Obama declared: "There was a time when they were saying North Carolina would be a 'game changer'."

He added: "Tonight we stand less than 200 delegates away from securing the Democratic nomination for President of the United States." Mrs Clinton referred at her rally in Indiana to Mr Obama's recent comment that Indiana would be a tie-breaker. "Tonight, we've come from behind, we've broken the tie and, thanks to you, it's full speed onto the White House."

She pleaded for more money, saying: "We can only keep winning if we keep competing against an opponent who outspends us massively." Behind her stood a tired looking Bill Clinton — he held nine campaign events in North Carolina on Monday — and their daughter Chelsea.

At the weekend, Mrs Clinton vowed to work "tirelessly" for Mr Obama if he became the nominee and last night she said: "I can assure you, no matter what happens, I will work for the Democratic nominee." Mrs Clinton vowed to continue, declaring: "Now it's on to West Virginia, Kentucky and the other states where people are eager to have their voices heard."

She also made clear her determination to continue the fight over the disputed elections in Florida and Michigan. With just six contests left, Mr Obama will emerge in June with the most elected delegates, although not enough to clinch the nomination. The race will almost certainly be determined by the party's 795 unelected super-delegates — the congressmen, senators, governors, former presidents and senior officials who can back either candidate.

One of her last remaining chances of swinging them her way was to win North Carolina and Indiana. David Axelrod, Mr Obama's chief strategist, said: "The reality of this is that Senator Clinton would have to win close to 70 per cent of the remaining delegates — that's a very tall order. We feel good about the position we are in."

Robert Gibbs, his communication director, said: "The finishing line is in sight. Yet as Mr Obama took another step toward the nomination, there were nevertheless strong signs that Democrats have become more polarised along race, class and gender lines than at any stage in his battle against Mrs Clinton, increasing concerns among party leaders that it can reunify for the general election.

In contrast to the scenes in Raleigh, the atmosphere at Mrs Clinton's rally in Indianapolis was subdued with little of the raucous chanting that marked victories in Ohio and Pennsylvania. Terry McAuliffe, Mrs Clinton's ever-ebullient national chairman, was determined to keep the focus on Indiana.

"Barack Obama said this state would be the tie-breaker. Well, the tie has just broken," he declared. Asked about Mrs Clinton's description of North Carolina as possibly "game-changing", he pointed to other looming contests in West Virginia, Kentucky and Puerto Rico "where we will win the popular vote".

He said super-delegates "have got to make their decision based on who is the best general election candidate". He added: "She wins in the states like Ohio we need in the general election." But Mr McAuliffe also conceded that May 31, when the Democratic Party's rules and bylaws committee meets to consider the vexed results of Florida and Michigan, is now "an important date".

He hinted at a possible compromise, saying that the Clinton camp might accept allowing back into the convention 50 per cent of the 366 delegates currently banned. Michigan and Florida were stripped of their delegates because they broke party rules by moving their primaries up the calendar.

Mrs Clinton won both states, but the candidates did not campaign in either state and Mr Obama's name was not on the ballot in Michigan. "If they had done what the rules say — and what the Republicans did — and taken away 50 per cent of the delegates, we would not have any argument."

Asked by The Times if he would settle for such a figure, Mr McAuliffe replied: "Let's see what happens on May 31." Mr Obama's victory in North Carolina was once again based on overwhelming backing from African-Americans. Over 90 per cent voted for him in the North Carolina, where 36 per cent of registered Democrats are black.

Fully 40 per cent of people who voted for Mrs Clinton in Indiana said that they would not vote for Mr Obama in the general election.

In both states, two-thirds of Mrs Clinton's supporters said they would be dissatisfied with Mr Obama as the nominee. In Indiana, as in North Carolina, over 90 per cent of African Americans backed Mr Obama. Over two-thirds of blue-collar whites in both states backed Mrs Clinton.

In North Carolina, Mrs Clinton won white women 63 per cent to 33, and white men 54 per cent to 40. Mr Obama overwhelmingly won the young, and the educated, upper income voting bloc.

Two-thirds of older voters backed Mrs Clinton. In both states, half of voters said the controversy over Mr Obama's former pastor had influenced their vote, although it is likely to have galvanised blacks to turn out for Mr Obama, while having the opposite effect for Mrs Clinton.

Paul Begala, a former adviser to Mr Clinton, and a supporter of Mrs Clinton, said of Mr Obama: "We can't win the White House with egg heads and African Americans." Donna Brazile, Al Gore's campaign manager in 2000 and an African American, retorted angrily: "Stop splitting us. Don't tell me I can't stand in Hillary's camp because I'm black."

Mrs Clinton's win in Indiana, and her overwhelming white support in North Carolina, will be used to bolster her argument that Mr Obama cannot win over enough white blue-collar voters, a key voting bloc, in a general election against John McCain.

Two of the next three contests are in West Virginia and Kentucky, states that favour the former First Lady. Yet she cannot ignore the fact the the arithmetic of the race and her failure to spring a surprise last night, leaves Mr Obama in a commanding position.