( dpa )- With Hillary Clinton and Barack Obama deadlocked after the biggest-ever round of US primary votes, Democrats on Wednesday faced the prospect of a drawn-out nomination fight between the two presidential hopefuls.
Some analysts believe that weeks of infighting between Obama and Clinton may divide the party and weaken its quest to retake the White House, even as resurgent US Senator John McCain works to unite Republicans behind his presidential bid.
Obama , seeking to become the first African-American president, said he was not worried, a day after claiming Super Tuesday victories in 13 states to Clinton's eight.
"I think it would be a problem if Senator Clinton's voters disliked me, or my voters disliked Senator Clinton," he said in Chicago. "I don't think that's the case."
Still, Clinton and her husband, former president Bill Clinton, have a reputation as tough campaigners. Obama's side has accused the Clinton camp of injecting race and personal attacks to try to undercut her rival's lofty talk of change and smoothing the nation's political divisions.
Clinton has also struggled to keep up with Obama's fundraising power, based on strong grass-roots organizing that has swept many voters into the political process. On Wednesday, she said she had loaned her campaign 5 million dollars of her own money.
"I loaned it because I believe very strongly in this campaign," she told reporters. "We had a great month fund-raising in January, broke all records. But my opponent was able to raise more money."
In the jockeying for the slightest edge, Clinton's camp challenged Obama to weekly televised debates in the buildup to March 4, when Democrats cast presidential preference votes in two key states, Texas and Ohio. Before that, the next major contest is next Tuesday in Maryland and Virginia.
Clinton, 60, and Obama , 46, traded notably bitter attacks in a January debate.
"And we would hope that Senator Obama would accept some debates, as many as four, between now and March 4th," said Howard Wolfson , Clinton's communications director.
Obama reacted cautiously, saying there would be more debates but "it's very important for me to spend time with voters."
On the strength of his Super Tuesday performance, Obama took a narrow lead over Clinton in the number of directly-awarded delegates to the Democratic Party's nominating convention in August, television networks reported.
The convention formally chooses the party's presidential nominee for the November 4 general election. But so-called superdelegates , which include Democratic elected and party officials and make up nearly 20 per cent of the total, may lean toward Clinton.
Obama insisted that he remains the underdog against the better-known Clinton, who spent eight years in the White House as first lady and is serving her seventh year as a US senator from New York.
She confidently reaffirmed her claim to front-runner status Wednesday, saying second place was not an option.
"I'm on the path to winning the nomination. We're in this, as I said at the very beginning, to win it," she said. "We are full speed ahead."
On the Republican side, McCain faced a different challenge: winning over core party supporters sceptical about his conservative credentials.
"Do we have a lot of work to do to unite the entire party? Sure," he said in his home state of Arizona. "After the campaigns are over, you've always got the task of uniting the party behind the nominee."
McCain, who would be the oldest US president to start a first term, staked a clear lead for the centre-right party's nomination, sweeping delegates Tuesday in the delegate-rich states of California, Illinois, New Jersey and New York.
McCain, 71, was the clear victor by percentage in nine of 21 Republican state contests. While the state victories give his campaign momentum, the bottom line is the number of delegates to the party nominating convention in September in St Paul, Minnesota.
He picked up 503 delegates Tuesday for a total of 615 since early January, CNN estimates showed. To win the nomination, he needs 1,191 delegates, or half the total.
Former Massachusetts governor Mitt Romney, 60, took seven smaller states, leaving him a distant second with 268 delegates. The big surprise was former former Arkansas governor Mike Huckabee , 52, a southerner and one-time Baptist minister who swept four Southern states Tuesday.