The folksy former Arkansas Gov. Mike Huckabee, who polled at just 5 percent in Iowa in early September, defeated millionaire Mormon businessman and former Gov. Mitt Romney's better-funded and more organized campaign.
"A new day is needed in American politics, just like a new day is needed in American government," Huckabee said after his victory, according to the Associated Press. "It starts here, but it doesn't end here. It goes all the way through the other states and ends at 1600 Pennsylvania Ave."
On the Democratic side, the 91 percent-white Midwestern state backed Barack Obama, the 46-year-old freshman senator from Illinois, a key first step in his effort to be the first African-American to secure a major-party presidential nomination.
Now that the pre-caucus hoopla has ebbed, candidates' attention turns to New Hampshire, Wyoming and the other 47 states that have yet to cast votes this primary season.
Obama managed to convince Iowans that he could shake up the Washington establishment, besting the promises of Sen. Hillary Clinton of New York and former Sen. John Edwards.
He told his supporters at a victory rally that they could some day "look back and say this is the moment where it all began," the AP reported.
"Barack Obama [is] a relative new face in American politics if you think about it," political analyst Stuart Rothenberg said Thursday night on the NewsHour. "Someone who ran on change and bringing the country together beats someone named Clinton? That's remarkable."
New York Times columnist David Brooks said on the NewsHour that Obama managed to convince Iowa's voters that his abstract visions for change have the necessary political might to win.
"Now his campaign is not just a crusade, it's not just about nice words like 'hope' and 'change.' It's actually a political movement," Brooks said. "And so now you had this idealism, which now has substance. And it's just big, it's a big event. I'd be stunned if he lost New Hampshire now." Clinton's campaign congratulated Obama, but promised the fight for the nomination was far from over.
"Our campaign was built for a marathon, and we have the resources to run a national race in the weeks ahead," Campaign Manager Patti Solis Doyle said in a prepared statement.
Romney, who polled ahead of the Republican pack for much of the past six months, said in his concession speech: "Well, we won the silver and congratulations to Gov. Huckabee for winning the gold. Nice job."
He added: "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're going to do."
On Thursday's NewsHour, Amy Walter credited much of Huckabee's success in Iowa to mobilizing the evangelical Christians.
"Something like 60 percent -- or over half of the voters -- identified themselves as evangelical Christians," she said. "Those are exactly the kind of people that Mike Huckabee has been appealing to and will continue to support him. We've been talking earlier about New Hampshire and the fact that it's much more secular. He's not going to be as successful there. But in South Carolina, that's absolutely the kind of place where that kind of coalition could also be helpful for him."
Analyst Stuart Rothenberg said he found it remarkable how Huckabee overcame a lack of presence in the Iowa polls in the spring to surge past Romney's political machine.
"This was supposedly an organization state," he said. "It was all about building a huge organization. Mitt Romney did that, yet Mike Huckabee ends up winning on momentum and message."
Huckabee understood a message of a leadership crisis in the U.S. would resonate with many voters, Brooks said on the NewsHour.
"People don't trust the government," he said. "They are suspicious of Wall Street and conservatives are suspicious of the leadership of the Republican Party. And Huckabee went after all three. They threw everything they had at him. And now, especially the Republican establishment, their weakness has been exposed.
"And then secondly," Brooks added, "he understood economic anxiety and the way [that] interplays with social anxiety. Divorce, family breakdown, mixing in with job losses and wages. And so he talked about a language of economics that was tied in with values, and those two things were huge."
Edwards, who has campaigned heavily in Iowa since 2005, also interpreted Thursday's vote as a call for a new political direction.
"What's clear from the Iowa caucus results is that change won and the status quo lost," Edwards told the AP. "And the fight is now to see if we are going to get the change we need to save the middle class in this country."