Older voters did not dominate the caucuses as they have in the past: Voters under 30 made up 23% of the people attending the Democratic caucus -- about the same percentage as those over 65.
Clinton, meanwhile, conceded she needed to do better among younger voters, but tried to turn the debate again to a question of competence and experience.
"This is especially about all of the young people in New Hampshire who need a president who won't just call for change, or a president who won't just demand change, but a president who will produce change, just like I've been doing for 35 years," she said.
Huckabee also polled well among young voters: 40% of voters between 17 and 24 entered the caucuses backing him.
One sign of the anti-establishment strain in the younger generation of Iowa Republicans: 21% of that age group supported Rep. Ron Paul of Texas, the long-shot candidate who has challenged his party's orthodoxy.
No one knows if youth turnout will be as much of a factor in other states. But one other source of Obama's strength -- independent voters -- surely will be. In Iowa, independent voters preferred him over Clinton by a margin of 41% to 17%. In New Hampshire, independents can vote in either party's primary, and polls indicate they are far more likely this year to vote in the Democratic contest.
Huckabee's challenge will be to expand his appeal to independents and more moderate conservatives. In Iowa, he dominated among conservative voters but lagged behind McCain and Romney among independents and voters who identified themselves as moderates.
In New Hampshire, Romney took the message of Iowa voters and tried to turn it to his advantage by casting McCain as the candidate of the status quo.
"The message I got out of Iowa," Romney told reporters, "was that people in Iowa said they want change. The two Washington insiders -- John McCain and Hillary Clinton -- both lost, John McCain by a lot."
Perhaps the biggest surprise of Iowa was that the call for change struck a chord among Republicans. It is a natural theme and impulse among Democrats because they are trying to replace a Republican president. But GOP candidates had to tread gingerly around President Bush to avoid alienating voters who still admire him.
But Huckabee was not shy about differing with Bush, and he openly challenged his party to pay more attention to lower- and middle-class families who are struggling in an economy most Republicans like to hail.
"The change message worked as well in the Republican primary as it did in the Democrats'," said GOP pollster Neil Newhouse, who is affiliated with no presidential candidate. "I thought populism won last night."
Times staff writers Michael Finnegan, Maria L. La Ganga and Peter Nicholas in New Hampshire contributed to this report.