Democrat Jeremy Goldberg greets friends at a fundraiser in Charlotte, N.C., on Wednesday. He is actively involved in fundraisers and Gen-0 (Generation Obama) issues and technology. (Linda Davidson/THE WASHINGTON POST)

It had been four years since they last gathered at a Democratic National Convention, but now it felt like much longer. The original two-dozen members of a grass-roots group in New York City called Generation Obama had grown older in ways that had to do with more than just age. They had wives and jobs and children. They spoke a little less about the “power of a movement” and a little more about the “hard responsibility of governing.”

Back in 2008, they had traveled together to Denver in a wave of euphoria to watch Barack Obama accept the Democratic nomination. Their group had spread across the country by then and grown into the thousands, coming to represent the youthful energy that helped propel Obama into office.

Now, in Charlotte, their group was representative of Obama’s youth support again: smaller, more realistic, more established and more fractious.

Some of the original members had become political insiders. Others had come to resent politics altogether.

The story of Generation Obama is the story of a key coalition in the 2012 presidential campaign. Many young voters were drawn into politics by this president, but now he is having trouble retaining their same level of support. It is a problem the Obama campaign has come to refer to as the “enthusiasm gap.” His staff is not so much worried about young voters favoring Mitt Romney, it is worried that the Obama volunteers of 2008 will turn into half-hearted voters and that the voters of 2008 will not bother to vote at all in 2012.

Obama continues to maintain a large lead over Romney with voters who are 18 to 29, but at no point in Washington Post-ABC polling of this race has he reached his level of support from 2008, when he was backed by 66 percent of young voters. Now, according to Post-ABC polling, about as many 18- to 29-year-olds hold “strongly negative” as “strongly positive” views of his work in office.

For the original members of Generation Obama, their response to the president is both more personal and more nuanced. His legacy is their legacy, they said. Like the president, they have grown older. Like him, they have wrestled with the hard gap between expectations and reality.

“There is a point where your idealism runs against the realism of politics,” said Jeremy Goldberg, 36, one of the co-founders of Generation Obama. “A lot of us have come to that point. That can drive you, but it can also demoralize you and make you tired.”

Goldberg started the group in 2007 over coffee with some friends, few of whom had ever been involved or interested in politics. They had watched Obama speak with his wife, Michelle, at a $100 fundraiser in New York City, and they wanted to help spread his ideals. They met every few weeks, hosting small parties for young professionals and sketching strategy on white boards in borrowed office space. Soon, their steering committee grew to 50 people; the Obama campaign started to solicit their advice; and the singer Ben Harper played at their fundraisers, calling Obama the future “greatest leader in the history of America.”

“At its heart, the group started with people who were attracted to the idea of Obama,” Goldberg said. “It was not so much about being part of a campaign but creating a collective movement.”

On Wednesday in Charlotte, Goldberg ran from one youth leadership meeting to another, gauging the legacy of the “movement” he had helped launch. Generation Obama had become Generation 44, now an official group run by the Obama campaign, with a polished Web site and a steady schedule of fundraising events across the country.

The group still included some of the core members of Generation Obama: a teacher, never involved in politics before Obama, who now raises funds for education reform on Kickstarter; a one-time marketing volunteer who was working full time for the campaign; and Goldberg, an entrepreneur in New York City who had flown to Charlotte to attend meetings on young voters, veterans’ benefits and policy in the Middle East.

Goldberg was in Charlotte with his wife two weeks ago, hoping to show her the community he had joined in 2008. As they traveled around town, he resisted the temptation to compare everything to “some kind of golden era,” he said, “to a time when literally everything seemed possible in a room of 40 or 50 people.”

He tried not to dwell on the fact that some of those people had moved on.

Sara Haile-Mariam, an activist from New York and a Generation Obama member, had started writing op-ed articles about her lack of engagement and keeping a personal blog. “The 2012 election cycle sucks,” she wrote. “Why? Because there is no real choice in this election.”

Matt Walters had traveled around the country with his then-girlfriend to knock on doors in 2008; now they were getting married and planning a honeymoon in Croatia, and the “events of our own lives have kind of taken over,” he said.

There was Arthur Leopold, once the most enthusiastic of them all, who had taken a semester off from school to help launch Generation Obama. He raised $1 million for Democrats in 2008 when he was only 20 years old, and called the convention in Denver “the most exciting point of my life.”

In the years since, Leopold graduated from Duke University and moved to New York. He took a job at an investment bank, where not everyone was so enamored with Obama and where he kept his politics close to the vest. He continued to support Obama but stopped raising money or obsessing over politics.

“The excitement or need to be there for the campaign just hasn’t really been there,” he said.

An old Obama acquaintance called to offer him a ticket to the convention in Charlotte. Leopold decided he couldn’t make it, so he offered the ticket to Cameron Chase, 22, an old friend from Duke. Chase, an Obama supporter who considered youth enthusiasm “pitiful” in this campaign, asked Leopold what would cause him to pass up a ticket to the convention.

“Life intervenes,” he said. “I’ve got a real job now, and I’ve got to go work.”

Jon Cohen contributed to this story.