During the past two months, Romney surrendered a double-digit lead in the polls, in part on the strength of Christian conservative support for Huckabee, a former Southern Baptist minister. Romney, trying to become the first Mormon president, has faced questions from some evangelicals who consider his faith a cult.
After being introduced by Dan Jansen, the speed skater who competed in four Olympic Games before winning a gold medal, Romney said in his concession speech: "Well, we won the silver and congratulations to Gov. Huckabee for winning the gold. Nice job."
Romney 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."
Romney insisted the Iowa results - with outsiders like Huckabee and him finishing one-two and freshman Illinois Sen. Barack Obama winning on the Democratic side - showed voters want change in Washington.
"We need new faces in Washington, and I intend to be one of them," Romney said.
Moments later, he departed for the airport and a late-night flight to New Hampshire, which votes. Jan. 8.
Romney's ads, criticizing Huckabee's pardons for prisoners and his position on illegal immigration, backfired with some caucus-goers.
"I was a Romney supporter, and then when the whole issue of pardons came up, I first was against Huckabee but then went back to him when I did more research and learned the full reasons why he released some people," said Colleen Vangore, 45, of Clive. "I felt that if Romney didn't tell me the whole story on that, there might be other things he wouldn't tell me the whole story on."
Romney addressed hundreds at Vangore's caucus site in this western suburb of the capital, and insisted he was in the race for the long haul.
"I hope Iowans makes a really powerful choice, and if you select me, I think I'll go on to become the nominee," he quipped. "If you don't, well, I'll still go on to become the nominee."
More than half of GOP voters said they were born again or evangelical Christians, and nearly half of them supported Huckabee, according to entrance interviews by The Associated Press and the television networks. Romney led among non-evangelical voters by 2-to-1 or more.
The voting in Iowa came exactly one year after Romney ended his only term in elective office, four years as governor of Massachusetts.
A multimillionaire who made his fortune as a venture capitalist, Romney spent about $7 million on ads in Iowa, compared to $1.4 million for Huckabee. He also raised and spent the most of any GOP contender, including at least $17 million of the fortune he built during a 20-plus year career as a businessman.