(CNN) -- Sen. Barack Obama claimed a significant victory in the South Carolina Democratic primary on Saturday, telling supporters "we are hungry for change."
The Illinois senator earned more than twice the vote that rival Sen. Hillary Clinton did, 55 percent to 27 percent, unofficial returns showed.
Former Sen. John Edwards was third with 18 percent.
"Tonight, the cynics who believed that what began in the snows of Iowa was just an illusion were told a different story by the good people of South Carolina," Obama said to supporters Saturday. Watch a recap of Obama's big win »
A win in South Carolina was considered crucial for Obama, who won Iowa but finished second to Clinton in New Hampshire and Nevada. See what the results mean »
"I did not travel around this state over the last year and see a white South Carolina or a black South Carolina. I saw South Carolina," he said.
"The choice in this election is not between regions or religions or genders," Obama said. "It's not about rich versus poor; young versus old; and it is not about black versus white.
"It's about the past versus the future." Watch Obama speech
With 99 percent of precincts reporting, Obama had 55 percent of the vote. Clinton was second with 27 percent, followed by Edwards, with 18 percent. Obama's victory capped a heated contest in South Carolina, the first Democratic primary in the South and the first with a largely African-American electorate.
Obama, who is hoping to become the the nation's first African-American president, did well with black voters, who made up about half of Saturday's electorate, according to exit polls.
Black voters supported the Illinois senator by a margin of more than 4-to-1 over his nearest rival, exit polls indicate.
Among white voters, Obama took about a quarter of the vote, with Clinton and Edwards roughly splitting the remainder, according to exit polls.
Clinton congratulated Obama and said she was excited to move forward to the Super Tuesday contests on February 5.
"Millions and millions of Americans are going to have the chance to have their voices heard and their votes counted," she told supporters at Tennessee State University. Watch Clinton speak to supporters »
Edwards also looked ahead to the next contests.
"Now the three of us move on to February 5, where millions of Americans will cast their vote and help shape the future of this party and help shape the future of America," he said. Watch Edwards rally supporters »
"Our campaign from the very beginning has been about one central thing, and that is to give voice to the millions of Americans who have absolutely no voice in this democracy."
Clinton beat Obama only among elderly voters, according to exit polls.
Among voters 65 and older, Clinton beat Obama 40 to 32 percent. But Obama handily defeated Clinton in every other bracket, and overall garnered 58 percent of the vote among 18 to 64-year-olds while 23 percent of those voters picked Clinton.
And half of those polled said both candidates shared blame for the rancor between the two camps. Of those who said one of the contenders was more to blame than the other, 21 percent blamed Clinton, and 6 percent said Obama.
"It's fairly obvious it's not going to be over February 5," Obama spokesman Robert Gibbs said.
Edwards was born in South Carolina and won the state's primary four years ago, when he was making his first bid for the White House. See voters head to the polls in South Carolina »
Edwards had touted his native status, and as the Clinton and Obama camps have squabbled, Edwards continued to talk about the issues and suggests he's the only adult in the field. Watch Edwards reach out to voters »
"I'm keeping moving no matter what, but I feel good about how things are moving right now here today," Edwards told reporters Saturday morning. "I feel there's a lot of energy behind my campaign."
On January 15, Edwards pledged, "I'm in this for the long haul. We're continuing to accumulate delegates. There's actually a very narrow margin between Sen. Obama, Sen. Clinton and myself on delegates."
The state Democratic party estimated that more than 530,000 Democrats turned out for Saturday's primary, as compared with 445,000 voters who showed up to vote last weekend in the state's Republican primary.
The Democratic numbers topped the GOP turnout for the first time since 1992, when 445,000 Republicans turned out to renominate President George H.W. Bush.
Obama attracted more than 290,000 votes -- nearly matching the total turnout of the 2004 Democratic primary.
"This is an enormous turnout," CNN analyst Jeffrey Toobin said. "Democrats are wildly motivated in this election."
As South Carolina's Democratic primary voters went to the polls Saturday, almost half of them had made up their minds more than a month ago, according to exit polls.
In the 2004 primary, nearly a quarter decided either the day of the primary or in the three days prior who they would support, but this year, only 10 percent of this year's voters waited until Saturday to choose.
Another 10 percent decided only in the last three days, and 32 percent decided in the last month.
Forty-seven percent made up their minds at least a month ago, more than double the percentage of 2004.
The early exit polls were taken from a sampling of 1,269 voters statewide.
Following a rough campaign between Clinton and Obama, the two camps toned down the rhetoric in the past two days, returning to the issues and concentrating their firepower on the Republicans rather than on each other.
"I think they [the Republicans] should be gracious and just say, "We have messed this thing up so much we are just going to quit and ... we shouldn't be re-elected,' but I don't think that is what they are going to do," Clinton said.
South Carolina is the last big test for the Democrats before Super Tuesday, February 5, when nearly two dozen states will hold either primaries or caucuses -- including such delegate-rich states as California, New York, New Jersey and Illinois.
Florida holds its primary on Tuesday but no Democratic delegates are being awarded there because the national party is penalizing the state for moving its primary up earlier in the year. E-mail to a friend
CNN's Paul Steinhauser, Bill Schneider, Peter Hamby, Alexander Mooney, Suzanne Malveaux and Jessica Yellin contributed to this report.
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