NEW YORK – Add this to President Barack Obama's problems in selling his health care overhaul: A lot of the tech-savvy activists who helped put him in office are young, feeling indestructible and not all that into what they see as an old folks issue.

It's a crucial gap in support and one the White House may have to correct if Obama is to regain the momentum and get Congress to act on his top domestic priority.

Matt Singer, a 26-year-old founder of the liberal group Forward Montana and an activist in the health care trenches, has tried to engage young people.

"Right now we're seeing a big conversation with seniors, but you're not seeing the same mobilization among young people who are President Obama's core constituency," Singer said. "The age demographic most supportive of reform has not been engaged, and it makes me very nervous."

Younger people are generally healthier and rely on less medical care, particularly young working men who make up the largest group that goes voluntarily without health insurance. They also are less likely to be as vocal at contentious town halls; many are either working or in school during the daytime forums.

Among senior citizens, the fear is palpable about Obama's efforts, reflected in public polling that shows support falling for his proposals. Seniors worry that paying for the $1 trillion-plus, 10-year overhaul will mean cuts in Medicare benefits.

Talk of death panels and "pulling the plug on grandma," although discredited, has scared seniors. Sensing opportunity, the Republican National Committee announced a "Seniors' Health Care Bill of Rights" Monday that pledges to protect the elderly from any attempt to ration health care because of age.

Seniors preferred Republican Sen. John McCain by a 55-43 percent margin in last year's general election — the only age group Obama lost.

Determined to energize his activist base, Obama talked up health care in an online town meeting last week with Organizing for America, the campaign operation reconstituted as the White House political arm. The operation has stepped up its push on health care, hosting thousands of events across every state and congressional district.

"It's great to be here with all of you because it reminds me of how we got here in the first place," Obama told the group in the meeting.

In an interview with radio talk show host Michael Smerconish, he also promoted his proposal for young people up to the age of 26 to get health coverage under their parents' insurance plans. "It gives them a way of having coverage until they get that job that has a little bit more security," he said.

Said Celinda Lake, a Democratic pollster who has researched the youth vote: "I think the White House thought they could mobilize their younger supporters just by saying, 'Come out.' But now they realize they have to run a real campaign."

The question is whether it's too late in the game for the 18-29-year-old voters who turned out in unprecedented numbers for Obama in 2008, giving him 66 percent of their vote to 32 percent for Republican McCain. Polling shows that younger voters are the most supportive of health care reform — but also the most likely to be uninsured.

Heather Smith, executive director of the youth-oriented group Rock the Vote, said that the heated arguments that have dominated the debate recently — from the future of Medicare to "death panels" to claims of rationing — have seemed far removed from the lives of young people, whose health-insurance worries primarily center on the cost and availability of coverage.

"What we've learned by working with this generation through polling is that attacks, rather than dialogue, doesn't attract them," Smith said. "Beyond the screaming, there's a tremendous amount of interest and concern among young people. It's just not something you see."

But critics also point to a failure of Obama's message, saying that by focusing so intently on the concerns of senior citizens the White House may have lost the attention of younger voters. They argue that the tools Obama used so successfully to mobilize young voters in the campaign, such as community organizing and social networking, need to be reintroduced and used more aggressively in this debate.

"If we're going to keep this generation engaged, we have to move away from the politics of partisan talking points and move back to what was done last year: the politics of engagement, citizenship, democracy, online and on the ground activity, and conversations with peers," Smith said.

Lake, the Democratic pollster, said the lack of involvement by young people in the health care push may hint at a bigger concern for the White House: Some so-called Obama "surge" voters, who voted for the first time in 2008 and are largely younger and nonwhite, may not be as motivated to get involved in his signature causes, including health care.

"They say, 'I'm taking a break from politics, I'm uninformed about the system, I'm sick of Washington, I'm not going to help these people.' It's interesting that he hasn't countered that disengagement," Lake said.

To bring those voters back, Lake said Obama needs to draw on his own personal popularity and make the health care debate about him, rather than allow it to seem like a mishmash of legislation coming out of Capitol Hill.

"He hasn't said yet, 'This is my plan. The opponents are trying to take my plan away from me,'" Lake said.

That's the argument Amanda Mack, a 27-year old organizer in South Dakota, says she makes when she urges young people to participate in the debate.

"During the campaign, young people got involved because they believed in Barack Obama and health care is something he made a priority," Mack said. She added that she expected to see more activity around the issue in the fall, when colleges are back in session and younger families return from vacation.

Singer, of Forward Montana, echoed that but said Obama must move quickly to inspire his core supporters.

"To win, you've got to turn out your base. In this case, it's the pragmatic youth who trust Barack Obama and say, 'This seems reasonable to me,'" Singer said.