MANCHESTER, New Hampshire (Reuters) - Democrat Hillary Clinton’s shocking loss to Barack Obama in Iowa punctured the air of inevitability her U.S. presidential campaign had sought to project and left her in the political fight of her life.

Democratic presidential candidate U.S. Senator Hillary Clinton (D-NY) speaks to supporters, after she placed virtually tied for second in the Iowa caucuses, at the Clinton headquarters in Des Moines, Iowa January 3, 2008. REUTERS/Brian Snyder (UNITED STATES)

The New York senator and former first lady, 60, must prove now whether she can get up after taking a punch. She faces her next test on Tuesday in New Hampshire, where fellow Democrat Obama, 46, has been threatening her lead in the polls.

Iowa was the first state contest for both the Democratic and Republican party nominations. The prize is valuable momentum and at least a temporary claim to the front-runner’s slot in the campaign ending in a November 4 election.

The winner of the November election will succeed George W. Bush as president in January 2009.

“I think she’s in a lot of trouble,” said Merle Black, a political science professor at Emory University in Atlanta.

“The Clinton campaign has to do a lot of rethinking now,” he said. “They’re not out of it, and she may be able to recover.”

Obama, a senator from Illinois who if elected would become America’s first black president, rode a message of change to win the lion’s share of Iowa’s mostly white Democratic voters over Clinton, who finished third, slightly behind former North Carolina Sen. John Edwards, 54.

“Our time for change has come,” an excited Obama told supporters after his victory became known.

Obama and Clinton have for months been locked in a classic battle in U.S. politics -- Obama’s promise to change the way Washington works versus the Clinton campaign’s self-described “strength and experience.”

CHANGE VERSUS EXPERIENCE

Obama vowed to open talks with leaders from hostile nations such as Iran, Cuba and Syria. Clinton and her husband, former President Bill Clinton, tried to raise doubts about Obama’s experience.

Bill Clinton scoffed at Obama as a risky, inexperienced choice, wondering aloud whether Americans would want to “roll the dice” on him.

In Iowa, change appeared to come out on top. Young people flocked to Obama’s camp in droves, compared to older Iowans who forged the base of Clinton’s support.

“I think Obama was able to generate some excitement about his candidacy that Clinton could just not generate and Obama’s sort of promise of something different was a little bit better than Clinton’s focus on experience,” said Peverille Squire, a political science professor at the University of Iowa.

New Hampshire will be critical for Clinton, and comparisons are inevitable to her and her husband, who finished second in New Hampshire in 1992 and declared himself the “Comeback Kid” after intense negative publicity about his marital infidelity and his military draft record.

The Clinton campaign, which has a strong national organization and is well-funded, tried to maintain a stiff upper lip and seemed eager to move on to other states.

“This race begins tonight and ends when Democrats throughout America have their say,” Clinton campaign manager Patti Solis Doyle said in a statement. “Our campaign was built for a marathon and we have the resources to run a national race in the weeks ahead.”

Edwards vowed to fight on despite finishing second -- sandwiched between Obama and Clinton -- in a state in which he has spent years wooing supporters.