Hillary Clinton and Barack Obama face weeks or even months of further campaigning after Super Tuesday left them in dead heat, with each candidate claiming an almost equal number of Democratic delegates.
Big victories moved John McCain closer to his party's nomination but a strong showing by Mike Huckabee and the survival of Mitt Romney ensured that the Republican race also remains unresolved.
Mr Obama yesterday claimed he had won more delegates than Mrs Clinton, although some delegates remained to be apportioned under the party's complex system of proportionate reputation. Despite claiming victory, however, Mr Obama sought to cling to the role of the underdog.
"We are less of an underdog than we were two weeks ago. Two weeks ago, we were a big underdog, now we're a slight underdog," he told reporters in Chicago.
Mr Obama won more states than Mrs Clinton but he failed to win any of Super Tuesday's biggest prizes, apart from his home State of Illinois. Mrs Clinton's wins included New York, New Jersey, Massachusetts and California, where polls had shown a huge surge for Mr Obama in recent days.
The race continues on Saturday with a primary in Louisiana and a caucus in Nebraska, followed next week by primaries in Virginia, Maryland and the District of Columbia. Mr Obama is well placed to win all of these contests and the next big victories Mrs Clinton is hoping for are in early March, when Texas and Ohio hold primaries.
The Clinton campaign admitted yesterday that it was running so short of cash that Mrs Clinton lent the campaign $5 million (€3.4 million) of her own money in late January. "The loan illustrates senator Clinton's commitment to this effort and to ensuring that our campaign has the resources it needs to compete and win across this nation. We have had one of our best fundraising efforts ever on the web today and our Super Tuesday victories will only help in bringing more support for her candidacy," the campaign said in a statement.
Mr Obama raised $32 million in January, compared to $13.5 million for Mrs Clinton. He can raise money more quickly because most of his donors have given small sums whereas many of Mrs Clinton's donors have already given the maximum allowed. Mr Obama suggested yesterday that he was better prepared to face the Republican nominee next November and he claimed that running against Mrs Clinton had tested his toughness.
"I assure you that having engaged in a contest against them for the last year that they've pulled out all the stops. And you know I think what is absolutely true is whoever the Democratic nominee is the Republicans will go after them. The notion that somehow senator Clinton is going to be immune from attack or there's not a whole dump truck they can't back up in a match between her and John McCain is just not true," he said.
Mr McCain urged conservative critics in his party to unite around him after his success on Tuesday, when he won almost twice as many delegates as Mr Romney and Mr Huckabee combined.
Mr Huckabee, whose surprise wins across the south have kept alive a campaign that appeared to be fizzling out, said he was determined to stay in the race. Mr Romney, who failed to make a breakthrough but won enough states to remain viable, said he was willing to go all the way to the national convention in September.
The Republican primary system, which usually awards all of a state's delegates to the winning candidate, could help Mr McCain to wrap up the nomination within the next few weeks if he continues to poll as he did on Tuesday.
