PORTSMOUTH, N.H. - President Obama launched a personal effort to reclaim the momentum for his health care initiative on Tuesday with a direct rebuttal of what he called "scare tactics," rumors and misrepresentations.

At a town hall that had the feel of a campaign rally, administration officials sought to tap the skill in confronting public doubts and fears that helped Obama win the White House.

"Every time we come close to passing health insurance reform, the special interests fight back with everything they've got," Obama told a civil but not necessarily friendly crowd of 1,800. "They use their influence. They use their political allies to scare and mislead the American people. They start running ads. This is what they always do. We can't let them do it again. Not this time. Not now."

Obama delivered the message as anger flared outside his event and at congressional town halls across the country -- sentiments that the president's advisers say they take seriously even as they decry what they view as a mix of genuine outrage and ginned-up activism.

Obama and his aides emphasized that Tuesday's town hall audience included skeptics. At one point the president asked that only people who disagreed with his approach raise their hand to be called on.

There were plenty who responded. A teacher from Portsmouth asked where the country was going to get the doctors and nurses to attend to all the newly insured people who would be seeking treatment. A man who identified himself as Bill Anderson said that Medicare tried to force him to take a generic substitute for Lipitor, the anti-cholesterol drug, which did not agree with him, before allowing him to return to the name-brand drug. Ben Hershenson, a self-described Republican -- "I don't know what I'm doing here" -- fretted that a government-run public option would kill private insurance companies.

Obama said that health reform would free doctors to concentrate on treatment because they would not be prodded to schedule unnecessary tests. He said Medicare's decision to allow Anderson to return to Lipitor showed that the system worked.

And he said that a government-run option should not kill private insurers, but rather force them to be more competitive. "UPS and Fed Ex are doing just fine," Obama joked in an example. "It's the post office that's always having problems."

Inside vs. outside crowds

Outside the school, things were less civil. There appeared to be about 2,000 people there, about 50 percent for and 50 percent against the Democrats' health reform plan. "Euthanize Obama!" yelled one protester at Tom Jordan, a teacher from Amesbury, Mass., who stood with the president's supporters and held up a "Euthanize Ignorance: Go Obama" sign.

In Pennsylvania on Tuesday, Sen. Arlen Specter, D-Pa., faced an unruly audience who booed and jeered. "You can do whatever the hell you please to do," one man yelled at Specter. "One day God's going to stand before you, and he's going to judge you and the rest of your damned cronies up on the Hill. And then you'll get your just desserts."

Senior adviser David Axelrod said the president had for weeks been "relishing" the opportunity to engage directly with people to defend his efforts to overhaul the nation's health care system, and he said the angry crowds at congressional town meetings do not reflect the larger society.

"Most Americans are interested and concerned about this issue and are listening intently," he said. "There are people on all sides of the debate who are a little over the edge. They tend to be the best TV."

Tuesday's town hall was the start of what White House officials promise will be a more pointed response to the crescendo of what Obama called "misinformation" coming from the critics of his reform efforts.

White House chief of staff Rahm Emanuel argued the contrast between Obama -- whom he described as "reasoned, calm, looking like an adult in the room" -- and some of the more bombastic protesters would also work to the administration's advantage in the debate.

On Friday, Obama is scheduled to hold a meeting in Bozeman, Mont., to discuss the plight of people dropped from their health insurance plans because of an illness. And at a third session on Saturday in Grand Junction, Colo., Obama intends to raise the subject of high out-of-pocket costs.

But many of Obama's closest advisers are also cautioning the president against panicking about the fate of his top domestic initiative. "The key here is to not overreact to the cable TV catnip of the moment and lose focus on the overall plan for passing comprehensive health insurance reform," Deputy Communications Director Dan Pfeiffer said.

The New York Times contributed to this report.