LAS VEGAS » For much of the presidential election of 2008, Barack Obama’s campaign was Emma Guerrero’s life. She was one of a dozen volunteers who showed up at an Obama campaign office here every night, taking time from her studies at the University of Nevada, Las Vegas, to be part of what she still remembers as the most exciting period of her life.

It was largely because of Guerrero — and hundreds of other college students like her across the country — that Obama assembled a formidable machine that helped him roll to victory in 2008, a triumph that included putting Nevada into the Democratic column for the first time in 12 years.

“We did everything,” she said. “We went canvassing. Phone banking. Cleaning the offices. Taking out my bosses’ dry cleaning. Whatever they needed. It was such an amazing time because we all believed and wanted him to get elected.”

Guerrero said that she did not blame Obama for the 13.4 percent unemployment rate that has gripped this state, and that she was still likely to vote for him. But as she looks to graduation this June and her job hunt ahead, the emotion she feels is fear, and she cannot imagine having the time or spirit to work for Obama.

“I don’t think I could do it anymore,” she said. “That campaign was an amazing experience. But I don’t think I’m in the same mind-set anymore. He hasn’t really addressed the young people, and we helped him to get elected.”

Across this state — and in others where young voters were the fuel of the Obama organization, voting for him 2-to-1 over John McCain — the enthusiastic engine of the 2008 campaign has run up against the reality of a deadened job market for college students.

Interviews here and across the country suggest that most of his college supporters of 2008 are still inclined to vote for him. But the Obama ground army of 2008 is hardly ready to jump back into the trenches, potentially depriving Obama of what had been an important force in his victory.

Obama’s advisers, while acknowledging the shift, said they were confident that the loss of these workers would be negated by an influx of new students who have turned of voting age since 2008. Obama’s campaign manager, Jim Messina, said there had been 8 million voters ages 18 to 21 registered since the last election, most of whom were Democrats.

“Their brothers and sisters started it, and they are going to finish it,” Messina said Monday. “They are storming into our office. Our volunteer numbers are up from where we thought they would be.”

Yet even Obama’s supporters say it seems unlikely that the president — given the difficulties of these past three years and the mood of the electorate of all ages — will ever be able to replicate the youthful energy that became such a defining hallmark of his campaign.

In the last election, Sandra Allen hosted a group of fellow Brown University students at her home to call voters in North Carolina and Indiana on Election Day, a common practice in the Obama campaign. Obama won those states to the shock of Republicans.

Asked if she would be doing similar work for Obama this time, Allen responded: “Not now. And I will not be streaking across the main green of any campus with hundreds of thrilled people were he to be re-elected next year.”

Allen graduated last year and, after surveying the job market, decided to take refuge in graduate school to wait things out.

“I’m not optimistic,” she said.

Jason Tieg, 22, a student at Brigham Young University-Idaho, voted for Obama with great enthusiasm in 2008. But now, struggling to find a part-time job to help him through school, is not even sure he would do that again.

“I got a job in July as a custodian on campus, but I lost it again when they needed to cut down,” he said.

“I don’t know if I’ll support him next year.”

It is hard to find a state that more vividly illustrates the danger to Obama from declining enthusiasm among young voters than Nevada. Few parts of the country have been harder hit by this recession, with stubborn double-digit unemployment, an unending wave of mortgage foreclosures and huge numbers of homeless. And there are few states where young voters were so crucial to Obama’s victory.

Mark Triola, who was president of Young Democrats of Nevada in 2008, said at the time, the Democratic organization at UNLV was about three times as big as the Republican organization. By last year, he said, they were about equal, a trend that students there say has not changed this year. (For his part, Triola graduated in the spring and found a job in the communications industry — “ideally probably not what I was looking for, but I don’t have any room to complain given what’s going on,” he said.)

Jolie Glaser, a gung-ho supporter of Obama in 2008 when she attended college here, has taken to doing volunteer work for a golf charity as she looks for a job in the nonprofit sector. Her enthusiasm for the president has dampened.

“It’s hard to be a passionate follower of him,” she said. “It’s easier to be a thoughtful supporter.”

Sarah Farr, 20, a communications student, could devote endless energy to helping Obama as a student here four years ago. But now, with graduation approaching in 2013, she said that was the last thing she and her friends who also worked for him were contemplating.

“I don’t have as much enthusiasm this time as I did last time,” Farr said. “Everybody is just focused on themselves and trying to get through school.”

“I’m scared that the major I’m getting won’t be helpful in the future,” she said. “That terrifies me. I’m terrified that by the time I graduate, there won’t be jobs. That’s very nerve-racking.”

And even those who remain strongly supportive of Obama here say they see little chance of his winning this state.

“I don’t think so, no,” said Maureen Gregory, 23, a Las Vegas native who turned up at an interview at Madhouse Coffee loaded with buttons, T-shirts and posters from the campaign. “People in Nevada are really angry. I think Nevada is going to be red again in 2012, definitely.”

In 2008 Gregory sneaked away from school every day to work at an Obama campaign headquarters.

“Sometimes I didn’t get out until midnight,” she said. She, too, could not imagine devoting that much time to him again, as much as she admires Obama.

“I didn’t think it was going to be so bad,” she said. “I’m looking for something to do. Even part time. I was definitely hoping Obama could do more.”