AARP members began filing scornful e-mail on the advocacy group's national Web site almost immediately after its leadership embraced a Republican-backed Medicare plan this week.

From one anonymous note among many, posted at 7:59 a.m. yesterday: "I am really upset that our policy makers in AARP have accepted in our name a prescription drug program that will help destroy Medicare as we know it."

And this at 8:35 a.m.: "This is the biggest sellout of any organization that purports to represent seniors."

At 10:56 a.m.: "I just canceled my membership a little while ago. I'm sure thousands more will be doing the same."

And on and on it went, phone and computer messages by the hundreds Monday night and yesterday, apparently from the ranks of the organization's 35 million members. Nearly all condemned the Washington headquarters and AARP Chief Executive Officer Bill Novelli for endorsing the $400 billion Medicare plan.

"We're catching hell for it," acknowledged Novelli, a Bridgeville native with a marketing background who vowed to increase AARP's aggressiveness when he took its helm two years ago.

He said late yesterday that the headquarters of the nation's biggest group representing older adults was receiving 200 phone calls an hour, and 50 members had canceled their memberships. He termed the number "50 too many," but not overwhelming.

"These are people upset for one of two reasons -- they don't think the drug benefit is good enough, or they've been led to believe this thing is going to threaten Medicare as they know it," Novelli said. "The latter is not true, but the former, they're right that it's definitely not perfect."

Aware of the criticism, AARP begins a $7 million television-newspaper advertising campaign today to support passage of the Medicare overhaul, emphasizing that it's the best possible compromise available now to help older Americans.

"We're going to have to do a lot of work to educate people about this thing," Novelli said. "What we're telling them is the proposed prescription drug Medicare bill isn't perfect, but millions of Americans can't afford to wait for perfect."

He will have a hard time selling even some of AARP's most active volunteers and supporters on that notion.

"They don't have the grass-roots support," said Theo McCracken of New Castle, a critic of the plan who is volunteer coordinator of federal issues statewide for AARP. "They should listen to the members, especially the volunteers, who would let them know how they feel about this thing."

Some congressional Democrats and other senior advocacy groups that are frequent allies of AARP also have expressed disappointment with the powerful organization, though its position was no shock after months of discussions. Those peer groups are unswayed by AARP's statements that it has to be moderate and bipartisan in the GOP-dominated Washington environment to accomplish any key goals -- particularly obtaining a long-sought prescription drug benefit for seniors.

"AARP has been working closely with the White House and Republican leadership on this bill, and it was clear what they wanted to do," said Edward Coyle, executive director of the smaller but politically feisty Alliance for Retired Americans. "But our members who are also AARP members are very upset with AARP for the position they've taken."

The members' comments posted on the AARP message board covered a wide range, both emotionally and factually.

Many didn't like the size of $35 monthly premiums and $275 deductibles for the drug benefit, and a gap in coverage that arises after $2,200 in drug costs. Others viewed facets of the program as benefiting private health insurers and pharmaceutical companies at the expense of consumers. An experimental program slated to offer private competition to Medicare in some markets in 2010 sparked fears of future benefit or service cuts.

Ray Landis, acting director of AARP's Pennsylvania chapter, said many people become more accepting of the changes once details are explained to them, but it's hard to satisfy everyone.

"When you have as big an organization as AARP is, there's people all over the place" philosophically, Landis said. "Especially among people that are active volunteers with us ... there's some obvious disappointment."

One of them is Jack Heim, 83, of Avalon, an activist for 20 years, most recently as the organization's Western Pennsylvania coordinator on federal issues. He's not going to cut up his membership card, and he tells other people to give the new program a chance, but he's disenchanted with his organization for getting so strongly behind a plan containing so many question marks.

"If Congress wants to pass it, leave them pass it, but AARP should say we're not in favor or just keep quiet," Heim said. "[Grass-roots members] don't feel AARP should spend millions of dollars backing this program."

He, McCracken and others say they're going to let their congressmen know that their positions differ with their national leadership on the issue. The gap between the positions of many AARP members and their leaders sparks reminders of the organization's worst public relations debacle, in 1988, when it had to backtrack on supporting legislation that increased premium costs for some elderly beneficiaries.

Novelli doesn't see the organization at that point.

"I expect there to be criticism," he said. "What we have to do is explain our position."