MANCHESTER, N.H. — Senator Clinton’s upset victory here last night reignites her candidacy and spreads the Democratic presidential race nationwide, as a suddenly unpredictable battle with Senator Obama heads to Nevada and then to South Carolina.

With 91% of the precincts reporting, Mrs. Clinton was defeating the freshman Illinois senator by two points in New Hampshire, 39% to 37%, despite polls in the final days showing Mr. Obama with as much as a 14 point lead. A former North Carolina senator, John Edwards, finished a distant third with 17% of the vote, with Governor Richardson of New Mexico coming in fourth with 5%.

The Clinton comeback reshapes a race that appeared heading rapidly Mr. Obama’s way after he raced by the former first lady in last week’s Iowa caucuses. Mrs. Clinton finished third, and her hopes for victory here seemed to diminish by the hour as momentum rushed to Mr. Obama.

A raspy Mrs. Clinton addressed a roaring crowd of supporters gathered in a gymnasium at Southern New Hampshire shortly after 11 p.m., saying she had a “very, very full heart.” She described her five-day campaign the Granite State as a revelatory experience. “In the past week, I have listened to you, and in the process, I have found my own voice,” Mrs. Clinton said.

The statement was a reference to the two moments that her advisers immediately described as turning points in her victory: a display of passion — some called it anger — as she made the case for her candidacy at a debate here on Saturday night, and a flash of emotion on Monday, when her eyes welled up and her voice cracked while she spoke to a group of undecided voters in Portsmouth.

The video clips were replayed constantly on cable news, and despite a debate over whether the display of emotion would help or hurt, her campaign said the answer was clear. “A whole lot of people saw her and said, ‘She’s just like me,'” a senior adviser to Mrs. Clinton, Ann Lewis, said after her victory.

One key to Mrs. Clinton’s win appeared to be a significant shift in support from women, who supported Mr. Obama in Iowa. Forty-five percent of women went with Mrs. Clinton in New Hampshire, to 36% for Mr. Obama, according to exit polls.

Addressing his supporters in Nashua, Mr. Obama congratulated Mrs. Clinton on her victory, but like he did in Iowa, he vowed to fight the “cynics” that he has said are standing against change. “We know the battle ahead will be long,” he said. “We have been told we cannot do this by a chorus of cynics and they will only grow louder and more dissonant in the weeks and months to come.”

He took on Mrs. Clinton’s criticism that he offered “false hopes.” “We have been warned against offering the people of this nation false hope,” he said. “But in the unlikely story that is America, there has never been anything false about hope.”

Last night’s result is a disappointment for Mr. Edwards, who edged out Mrs. Clinton in Iowa. The finish will raise doubts about his viability, but he pledged to soldier on last night.

“Up until now, about one half of one percent of Americans have voted,” he told supporters. “Ninety-nine percent plus have not voted, and those 99% deserve to be heard.”

With polls looking grim yesterday, the Clinton campaign was dampening expectations and girding for a second straight primary loss. They were planning shifts in strategy well before the polls closed in New Hampshire. One move, according to a source close to the campaign, will be to make a greater and more public use of prominent minority supporters in an effort to blunt Mr. Obama’s momentum with black and Hispanic voters. Those surrogates include but are not limited to the mayor of Los Angeles, Antonio Villaraigosa; the lieutenant governor of Maryland, Anthony Brown; the lieutenant governor of New York, David Paterson, and the president of the Bronx, Adolfo Carrion.

Inaninterviewbeforelastnight’s results were in, Mrs. Lewis would not confirm reports that a former chief of staff to Mrs. Clinton in the White House, Maggie Williams, had been tapped to join her campaign. And she downplayed the suggestion that Mrs. Clinton’s staff was set for a shake-up. “We’re not shaking up; we’re gearing up,” she said in an interview.

Mrs. Clinton took a much more aggressive tone vis à vis Mr. Obama in the five days since she finished a disappointing third place in the Iowa caucuses. She and her surrogates have criticized Mr. Obama for changing his positions on key issues, and on Monday, she belittled his attempt to compare himself to the Reverend Martin Luther King Jr.

The victory of Mrs. Clinton can also be attributed, in part, to her tremendous field organization. Almost unnoticed amid the fervor around Mr. Obama’s campaign was the commitment the campaign made to identifying its voters and getting them to polling places. The campaign boasted of more than 6,000 volunteers, who knocked on what the campaign described in a quiet press release Monday as “tens of thousands of doors.” The release trumpeted the backing of such celebrity backers as the former chairman of the Democratic National Committee, Terry McAuliffe, and Mr. Villaraigosa of Los Angeles.

Boston’s mayor, Thomas Menino, dispatched roughly 150 volunteers to the voter-rich districts of Manchester for four straight days. The volunteers worked in shifts, sometimes going back multiple times to the same house. The targets were voters who, while they expressed either a slight preference for Mrs. Clinton or were undecided, were deemed voters for whom a reminder was required for them to come out and vote.

The result of this: a group of voters who would be undercounted by pollsters arriving at polling places on Election Day, including older women, people with canes and walkers. Mother Nature also provided a boost.

Many of these voters would have been unlikely to get to voting sites had the weather been frigid and icy as it has been on many New Hampshire days in recent weeks and not a sunny, balmy day in the 60s.

Mrs. Clinton returns to New York today, while Mr. Obama will hold a fund-raiser in New York and a rally in Jersey City, N.J.

The question for the Clinton campaign coming out of the Granite State will be how far she should go in confronting Mr. Obama, whose campaign has been compared in recent days to a phenomenon not seen in decades. Ms. Lewis and other supporters expected Mrs. Clinton to continue to make a strong case against the freshman Illinois senator, but some warned against going negative.

“Mr. Obama is a very popular candidate. Negative ads will probably backfire,” a former member of the Boston City Council campaigning for Mrs. Clinton in New Hampshire, John Nucci, said.

Mrs. Clinton spent the first half of the day greeting supporters at polling places.

At the Broken Ground School in Concord, she did not appear overly concerned with picking up lastminute votes, mostly posing for pictures with children. Offered encouragement by one supporter on a rope line, she replied: “I think we’re finally going to have a real election.”

She was joined by her daughter, Chelsea, who had mixed success with voters. After greeting 18-year-olds Patrick Dillon and Drew Burger, she asked them if they planned to vote. They said they did. “Oh, nice, so you’re voting for my mom?” Ms. Clinton asked. Messrs. Dillon and Burger fell silent. “Ah, you’re keeping me in suspense,” Ms. Clinton said, moving down the rope line.

Asked whom he was going to vote for, Mr. Burger said he was undecided, but he added: “I’m almost positive I’m not going to vote for Chelsea’s mom.”

At precincts in Concord and Manchester, several voters said they had changed their mind since the Iowa caucuses, but not all of them followed the momentum wave to Mr. Obama. A Manchester resident, Bonnie Paine, 44, said she was “truly undecided” but was moved by seeing video of Mrs. Clinton becoming emotional at an event yesterday in Portsmouth as she discussed the rigors of the campaign.

For Ms. Paine at least, it made her decision. “It touched my heart,” she said. “I was waiting for one moment of being inspired. That was the moment.”