PORTSMOUTH, N.H. — President Bush and his allies are working hard to nullify the power of the AARP, the mighty lobby for older Americans that is the archenemy to his Social Security plan.

Everywhere he goes, Bush promises the group's members they won't be touched by his plan, while his backers say the AARP is out of touch and prone to scare tactics.

Polling makes clear that young people like Bush's plan for personal accounts in Social Security while older people don't, so Bush is hoping to shift the debate toward the young.

In an airport hangar here, college senior Amy Partin joined the president onstage to serve as a human reminder of the future. Bush hit his central message over and over — people older than 55 would not be affected by changes he's proposing. He used the phrase "nothing changes" four times.

"Once the seniors realize nothing changes, the voices you'll hear from are the Amys of America," Bush told 2,000 people assembled recently for one of a string of campaign-style events pitching his Social Security plan.

At the same time, conservatives allied with Bush are trying to undercut the AARP.

"AARP doesn't care about the children or grandchildren of their own membership, and I think that's very shortsighted," Sen. John Sununu, R-N.H., contended yesterday.

Last week, House Majority Leader Tom DeLay called the group's opposition to personal accounts hypocritical, adding that it sells mutual funds to its members.

And a group that bills itself as an alternative to the AARP, USA Next, has run Internet ads suggesting the AARP is a liberal front for everything from gay marriage to gun control, and the group's leader says a wave of direct mail, TV and radio ads are coming next.

It's risky. Polling shows the AARP is more respected than any other voice in the Social Security debate, including Bush, Federal Reserve Chairman Alan Greenspan and congressional leaders of both parties.

"Going after the AARP is nuts," said Republican strategist Ed Rollins, who recently conducted a bipartisan poll on Social Security. "Don't make them the enemy."

The AARP agrees with Bush that Social Security faces long-term problems and says it wants to be part of the discussion about how to fix them. But it deeply opposes the centerpiece of the Bush plan: allowing younger workers to divert a portion of their Social Security payroll taxes into personal accounts that could be invested in the stock market in trade for reduced guaranteed benefits.

The group has spent $10 million in newspaper advertisements advising: "If you have a problem with the sink, you don't tear down the entire house."

Polling finds that overall support for the Bush plan is falling, though younger people are more supportive than older people. With this in mind, the AARP is planning television and radio ads targeted toward young people.

Bush's effort to undercut the AARP is subtle, simply promising older people that their benefits are safe. The AARP responds that Bush might mean that, but he can't guarantee it. They say that his plan for private accounts will cost so much money — up to $2 trillion — that it will create pressure on the government to cut spending, perhaps including benefits for current retirees.

Even if seniors are protected, many still care enough about Social Security to get involved in the debate. It's not simply a matter of self-interest, said Jon Krosnick, a political psychologist at Stanford University.

"Older people care about other old people, as well as everyone else who will be old in the future," he said. "Many of them understand the political power they have as a group."