(Adds vote count, details)
By John Whitesides, Political Correspondent
WASHINGTON, May 13 (Reuters) - Hillary Clinton scored a big victory over front-runner Barack Obama in West Virginia on Tuesday, although it could be too little and too late to stop his march to the Democratic presidential nomination.
Clinton hoped the landslide win in a state dominated by the white working-class voters who have been her biggest supporters would turn around her campaign and bolster her case that she is the Democrat with the best chance to beat Republican John McCain in November’s election.
Obama, who would be the first black U.S. president, retains a nearly insurmountable advantage in delegates who will select the nominee at the party convention in August. West Virginia had only 28 delegates at stake.
Clinton vowed to keep fighting until the Democratic voting ends on June 3 despite her dwindling prospects and a mounting campaign debt.
“I am more determined than ever to carry on this campaign until everyone has had a chance to make their voices heard,” Clinton told a victory celebration in Charleston, West Virginia.
“This race isn’t over yet. Neither of us has the total delegates it takes to win,” the New York senator and former first lady said, adding: “We are in the home stretch.”
Clinton, whose campaign is at least $20 million in debt, appealed for money to keep her White House bid alive.
“I’m asking people to think hard about where we are in this election, about how we will win in November,” she said, noting her strength in big states like Ohio and Pennsylvania that are critical in a presidential election.
With over half of the votes counted in West Virginia, Clinton led Obama by more than 35 percentage points.
Obama, who made only one brief campaign stop in West Virginia before the contest, visited the general election battleground of Missouri on Tuesday. He already was looking ahead to a November match-up with McCain.
“A vote for John McCain is a vote for George Bush’s third term,” Obama said in Cape Girardeau, Missouri. “We cannot afford any more of the Bush-McCain program.”
Obama did not appear in public after the voting ended in West Virginia, but a campaign spokeswoman said he left Clinton a congratulatory message on her mobile phone. He is scheduled to make stops in the general-election battleground states of Michigan on Wednesday and in Florida next week.
A delegate count by MSNBC gives Obama 1,880 delegates to Clinton’s 1,718 with six more delegates to be awarded in West Virginia. That leaves him 145 short of the 2,025 needed to clinch the nomination.
Neither candidate can win without help from superdelegates — nearly 800 party officials who are free to back any candidate. Obama has been gaining ground among superdelegates for weeks and picked up four more on Tuesday.
He now has a narrow lead over Clinton among superdelegates with fewer than 250 still to be named or uncommitted.
“Barack Obama leads in pledged delegates, contests won and superdelegates. And for perspective, while 28 pledged delegates are up for grabs this evening, Obama has won the support of 27 superdelegates in the course of just the last week,” an Obama campaign memo said.
A newly announced Obama supporter, former Colorado Gov. Roy Romer, declared it impossible for Clinton to catch Obama. “The math is controlling. This race, I believe, is over,” he said on a conference call sponsored by the Obama campaign.
Exit polls showed Obama picked up more than a quarter of the white vote in West Virginia, which has a small black population. Two of every 10 white voters said race was a factor in their vote, and only a third of those said they would support Obama against McCain.
About half of West Virginia voters said they believed the Illinois senator shared the views of the Rev. Jeremiah Wright, his controversial former pastor.
Five more contests remain in the Democratic nominating battle, with a combined 189 delegates at stake. Oregon and Kentucky vote on May 20, Puerto Rico votes on June 1 and Montana and South Dakota vote on June 3.
Clinton is favored again next week in Kentucky and Obama is favored in Oregon. (Additional reporting by Deborah Charles, Jeff Mason, Rick Cowan and Andy Sullivan; Editing by Chris Wilson) (To read more about the U.S. political campaign, visit Reuters “Tales from the Trail: 2008” online at http:/blogs.reuters.com/trail08/)