DES MOINES, Iowa (CNN) -- Barack Obama and Mike Huckabee have claimed victories in Iowa's first-in-the-nation caucuses.
With all Democratic precincts reporting, Obama had the support of 38 percent of voters, compared to 30 percent for John Edwards and 29 percent for Hillary Clinton.
"The numbers tell us this was a debate between change and experience, and change won," said CNN political analyst Bill Schneider.
Iowa delivered fatal blows to the campaigns of Sen. Chris Dodd of Connecticut and Sen. Joe Biden of Delaware. Both have decided to abandon their White House runs.
New Mexico Gov. Bill Richardson, who finished fourth, said his campaign plans to "take the fight to New Hampshire."
New Hampshire holds the nation's first primary Tuesday.
Clinton and Obama are in a statistical dead heat in New Hampshire, according to the latest CNN/WMUR poll. Watch where millions of dollars and months of campaigning have left candidates »
On the GOP side, Sen. John McCain of Arizona, whose campaign was languishing six months ago, and former Massachusetts Gov. Mitt Romney are now tied for first place in New Hampshire, according to the poll, which was released Wednesday.
McCain left Iowa before caucus night even began. He was already in New Hampshire by Thursday afternoon, trying to get a jump on his rivals.
For the winners of both party's caucuses in Iowa, it's an age revolt for Democrats versus a religious revolt for Republicans, Schneider said.
Among Democrats, Obama took 57 percent of the under-30 vote, according to CNN's analysis of entrance polls. Watch Obama celebrate his victory
Speaking to supporters, Obama called the night a "defining moment in history."
"You came together as Democrats, Republicans and independents to stand up and say that we are one nation, we are one people and our time for change has come." Watch an audio slideshow of the candidates' speeches »
Huckabee's victory can be attributed to his overwhelming support among evangelical voters and women, the polls indicate.
With 92 percent of Republican precincts reporting, Huckabee, former governor of Arkansas, had the support of 34 percent of voters, compared to 25 percent for Romney. Fred Thompson had 13 percent, McCain had 13 percent and Ron Paul had 10 percent. What do the results mean? »
Former New York Mayor Rudy Giuliani, who has turned the focus of his campaign to the February 5 "Super Tuesday" primaries, trailed with 4 percent.
"We've paid a lot of attention to states that some other candidates haven't paid a lot of attention to," Giuliani said, adding, "Time will tell what the best strategy is." Watch Giuliani describe his strategy »
Huckabee was vastly outspent by Romney, who poured millions of dollars into a sophisticated get-out-the-vote operation.
"People really are more important than the purse, and what a great lesson for America to learn," Huckabee said in thanking his supporters. Watch Huckabee claim victory »
For most of 2007, Huckabee languished in the single digits in the polls and had very little success raising money. But his momentum picked up in the final six weeks of the year when social conservatives -- an important voting bloc in Iowa -- began to move his way.
"We won the silver ... You win the silver in one event. It doesn't mean you're not going to come back and win the gold in the final event, and that we are going to do," Romney said.
Clinton, speaking with 96 percent of the vote in, portrayed herself as the candidate who could bring about the change the voters want.
"I am so ready for the rest of this campaign, and I am so ready to lead," she said.
Clinton had worked to convince Iowa caucus-goers she has the experience to enact change, while Edwards and Obama preached that she is too much of a Washington insider to bring change to the nation's capital.
"Now we move on ... to determine who is best suited to bring about the changes this country so desperately needs," he said.
McCain, who had largely abandoned Iowa to focus on the New Hampshire primary, said, "The lessons of tonight's election in Iowa are that one, you can't buy an election in Iowa; and two, that negative campaigns don't work." Watch what McCain says about the results »
With such a close race on both sides, voter turnout was key. The Iowa Democratic Party reported seeing record turnout. The party said there were at least 227,000 caucus attendees. The Iowa GOP projected that 120,000 people took part in the Republican caucuses. See how candidates courted voters »
The Iowa Democratic Party said 124,000 people participated in the 2004 caucuses, while the Republican Party of Iowa estimated that 87,000 people took part in the 2000 caucuses. (President Bush ran unchallenged for a second term in 2004.)
Caucus-goer Kathy Barger, inside a Democratic caucus site in Walnut, Iowa, said the room she was in was packed to the brim with a line out the door. Watch what it was like inside the caucus »
"I don't know how they are going to be able to fit everybody in the room, much less count the votes," she said. "There are bodies in every available space in the room."
The White House hopefuls campaigned down to the wire in Iowa, determined to reach as many people as possible before the 1,781 caucuses that started at 7 p.m.
Iowa Democrats, unlike Republicans, use a more complicated system to determine a candidate's viability. Republican caucus-goers are asked for their support for a candidate only one time during the event. Democrats are asked twice: an initial question of support, and a second if their first-choice candidate does not reach a 15 percent threshold to achieve viability.
Among Republican candidates, Thompson, a former senator from Tennessee, and Rep. Duncan Hunter of California needed strong showings in Iowa to keep their campaigns going, while Paul, a representative from Texas, is likely to ride his surge of popularity through February 5 -- "Super Tuesday," when 24 states hold their primaries -- no matter where he places in the early contests. E-mail to a friend
CNN's Mark Preston, Peter Hamby, Dana Bash and Candy Crowley contributed to this report.