DES MOINES, Iowa – Sen. Barack Obama swept to victory in the Iowa caucuses Thursday night, pushing Hillary Rodham Clinton to third place and taking a major stride in a historic bid to become the nation’s first black president. Mike Huckabee rode a wave of support from evangelical Christians to win the opening round among Republicans in the 2008 campaign for the White House.

Obama, 46 and a first-term senator from Illinois, told a raucous victory rally his triumph showed that in “big cities and small towns, you came together to say, ‘We are one nation, we are one people and our time for change has come.'”

Nearly complete returns showed the first-term lawmaker gaining 37 percent support. Former Sen. John Edwards of North Carolina appeared headed for second place, relegating Clinton, the former first lady, to a close third.

Huckabee celebrated his own victory over Mitt Romney and a crowded Republican field. “A new day is needed in American politics, just like a new day is needed in American government,” the former Arkansas governor told cheering supporters. “It starts here but it doesn’t end here. It goes all the way through the other states and ends at 1600 Pennsylvania Avenue.”

Huckabee, a preacher turned politician, handily defeated Romney despite being outspent by millions of dollars and deciding in the campaign’s final days to scrap television commercials that would have assailed the former Massachusetts governor. His triumph more robust than Obama’s, he was winning 34 percent support, compared to 25 percent for Romney. Former Sen. Fred Thompson and Sen. John McCain battled for third place.

With the New Hampshire primary only five days distant, Clinton and Edwards vowed to fight on in the race for the Democratic nomination.

“We have always planned to run a national campaign,” the former first lady told supporters at a noisy rally attended by her husband and their daughter, Chelsea. “I am so ready for the rest of this campaign, and I am so ready to lead.”

Edwards, the Democrats’ 2004 vice presidential nominee, told The Associated Press in an interview he would distinguish himself from Obama in New Hampshire by arguing that he is the candidate who can deliver the change that voters have shown they want. “I”m going to fight for that change,” he said by telephone from his hotel room in Iowa. “I’ve fought for it my entire life. I have a long history of fighting powerful interests and winning.”

Not everyone was going on. Officials said Democratic Sens. Christopher Dodd of Connecticut and Joseph Biden of Delaware were leaving the race after failing to generate appreciable support in Iowa.

Romney sought to frame his defeat as something less than that, saying he had trailed Huckabee by more than 20 points a few weeks ago. “I’ve been pleased that I’ve been able to make up ground and I intend to keep making up ground, not just here but across the country,” he said.

The words were brave, but already, his strategy of bankrolling a methodical campaign in hopes of winning the first two states was in tatters – and a rejuvenated McCain was tied with him in the polls in next-up New Hampshire.

Iowans rendered their judgments in meetings at 1,781 precincts from Adel to Zwingle, in schools, firehouses and community centers where the candidates themselves could not follow.

With President Bush constitutionally unable to seek re-election, a wide-open race developed in both parties and produced a record turnout.

Projections estimated that 220,588 Democrats showed up on a cold midwinter’s night, shattering the previous mark of 124,000.

Turnout was also up on the Republican side, where projections showed about 114,000 people taking part. The last previous contested Republican caucuses in 2000 drew 87,666 participants.

In interviews as they entered the caucuses, more than half of all the Republicans said they were either born-again or evangelical Christians, and they liked Huckabee more than any of his rivals. Romney led handily among the balance of the Iowa Republican voters, according to the survey.

About half the Democratic caucus-goers said a candidate’s ability to bring about needed change was the most important factor as they made up their minds, according to the entrance interviews by the AP and the television networks. Change was Obama’s calling card in the arduous campaign for Iowa’s backing.

Obama also outpolled Clinton among women, and benefited from a surge in first-time caucus-goers. More than half of those who participated said they had never been to a caucus before, and Obama won the backing of roughly 40 percent of them. Edwards did best among veteran caucus-goers, garnering 30 percent of their vote. Obama and Clinton each got about a quarter of their support.

An AP analysis of Iowa’s Republican caucuses estimated that Huckabee would win 30 delegates to the national convention and Romney would win 7.

Obama’s victory was much narrower in the race for delegates. The AP analysis estimated Obama would win 16 delegates, compared to 15 for Clinton and 14 for Edwards. Clinton will win more delegates than Edwards, despite getting fewer votes, because of Iowa’s complicated caucus system.

In the overall race for the nomination, Clinton leads with 175 delegates, including superdelegates, followed by Obama with 75 and Edwards with 46.

While Republicans and Democrats both looked to Iowa to pass the first judgment of the election year, there was a key difference in the way they ran their caucuses. Republicans took a straw vote, then tallied the results. Democrats had a more complicated process in which one candidate’s supporters might eventually wind up backing another contender.

Clinton, Obama and Edwards had all urged voters to consider them if their own candidate fell short. Rep. Dennis Kucinich of Ohio publicly urged his backers to line up with Obama on a second round, and two Democrats said aides to New Mexico Gov. Bill Richardson did likewise as the caucuses unfolded. Those two spoke on condition of anonymity, citing private discussions.

With President Bush constitutionally barred from seeking re-election, both parties had wide-open, costly campaigns.

Obama, a first-term senator, stressed a need for change. Clinton boasted of her experience as she worked to follow her husband into the White House. Edwards cast himself as the implacable enemy of special interests as he aimed to improve on last time’s second-place showing in the state.

Romney, a former Massachusetts governor, stressed his background as a businessman and organizer of the 2002 Olympics, and he worked to persuade conservatives to ignore his earlier positions on abortion and gay rights. He ran the only commercials of the campaign critical of a rival, hitting Huckabee for his positions on immigration and the pardons he issued while governor of Arkansas.

For three decades, Iowa’s caucuses have drawn presidential hopefuls eager to make a strong first impression, and this year was no different.

Obama, Clinton and Edwards spent at least $19 million on television advertising among them, and all three capped their campaigns with statewide broadcasts on Wednesday. Romney told supporters in a final daylong swing around the state he had been in 68 of 99 counties since he began his quest for the White House, had spent 55 days in Iowa and spoken before 248 separate audiences.