WASHINGTON - Democratic Sen. Hillary Rodham Clinton must win 57 per cent of the remaining primary and caucus delegates to erase Barack Obama's lead, a daunting task requiring landslide-sized victories by a struggling presidential candidate.
Obama's victories in Wisconsin and Hawaii on Tuesday -- his ninth and 10th in a row -- left him with 1,178 pledged delegates won in primaries and caucuses in The Associated Press' count. Clinton has 1,024.
Another 1,025 remain to be awarded, most of them in contests in 14 states, Guam and Puerto Rico. It takes 2,025 to win the nomination.
Further complicating Clinton's challenge, Obama appears particularly well-positioned to win at least one of the remaining states with ease. Mississippi, with a primary on March 11, fits a pattern of Southern states with large black populations that he has won handily, including South Carolina, Alabama, Georgia and Louisiana.
The rival campaigns maintain their own delegate counts. And while both agree Obama is the leader, they differ on the significance.
"The only way in this system to amass delegates is to win by big margins. Close races result in close delegate distribution," David Plouffe, Obama's campaign manager, told reporters in a conference call.
"The only way she can do it is winning states like Ohio 65-35, Texas 65-35, Pennsylvania, you know, 70-30. and you go on and on and on. She'd have to win pretty much all the states, even states where we're considered to have some strength," he added.
Clinton's top aides said Plouffe was deliberately trying to set unrealistically high expectations for the former first lady.
"We expect to do well in both those states," said Harold Ickes, speaking of Texas and Ohio, which hold primaries on March 4. "But 65 per cent is a far reach and there is no expectation here that we're going to hit that number."
"We're in the neighborhood of about 75 delegates behind, that is less that 3 per cent of the total number of delegates who have been elected. We expect to narrow that gap substantially by the end of this process," he added.
Obama's lead in delegates won at the ballot box is partially offset by Clinton's advantage among superdelegates -- members of Congress, governors and other party leaders who are unpledged to either candidate. She leads in that category, 238-173, cutting Obama's overall margin to 89 delegates in the AP count.
Superdelegates are free to shift allegiances. And Clinton's recent string of primary and caucuses defeats coincides with a slow erosion of support among the same party leaders who established her as the front-runner months before the first votes were cast.
She has failed to add any since Super Tuesday on Feb. 5, while Obama is slowly gaining ground.
The former first lady lost two more superdelegates during the day, both in New Jersey, when one switched to Obama and the other moved to uncommitted.
Additionally, Reps. Lloyd Doggett of Texas and Ron Kind of Wisconsin, both superdelegates, endorsed Obama.
"My constituents overwhelmingly chose Barack Obama to be their nominee, and I am proud to pledge my superdelegate vote to him as well," Kind said in a statement.
Further underscoring Clinton's political peril, Rep. David Scott of Georgia announced he would vote for Obama rather than the former first lady, and Rep. John Lewis said he might switch, as well.
Superdelegates aside, results in earlier states show how difficult Clinton will find it to overtake Obama's lead when the primaries resume in two weeks.
In general, delegates are allocated on the basis of popular votes within congressional districts, and any candidate who gains 15 per cent of the vote is entitled to at least one.
Clinton won New Jersey with 54 per cent of the vote and Massachusetts with 56 per cent on Feb. 5. But because Obama ran relatively well, particularly in some congressional districts, she won the delegate competition by only 28 delegates combined in the two states.
Contrast that to Obama's home state of Illinois, he won slightly less than 65 per cent of the vote -- and won 55 more delegates than Clinton.
The contests left on the calendar include primaries in Ohio, Texas, Vermont, Rhode Island, Mississippi, Pennsylvania, Indiana, North Carolina, West Virginia, Kentucky, Oregon, Montana and South Dakota as well as caucuses in Wyoming, Guam and Puerto Rico. There are 44 delegates unallocated from primaries and caucuses held earlier.
