WASHINGTON – Most Americans haven’t heard of John Rother, but he may have more influence than most senators when it comes to the future of Social Security.

As the policy director and chief lobbyist for the powerhouse seniors’ lobby group, AARP, the soft-spoken 58-year-old is the force behind the group’s loud, multimillion-dollar hard line against the president’s proposed overhaul of Social Security.

“We will do whatever it takes” to defeat President Bush’s accounts plan, Mr. Rother told The New York Sun in a recent interview.

To date, the AARP has been one of the harshest and most effective critics of the administration’s proposal to divert Social Security taxes into private accounts. It has run ads comparing the plan to casino gambling and flattening a house to repair a clogged sink.

Yet he has Democratic opponents of private accounts worried, too. They privately fear the AARP may take a similar tack with accounts as it did with the Medicare prescriptions drug benefit: oppose it for a while and then shock its ostensible allies by cutting a deal that allows the administration to claim a victory.

The nonpartisan group claims it is not concerned with making Democrats or Republicans look good, that its aim is the long-term solvency of America’s largest entitlement program.

Mr. Rother has met with the president personally to discuss the issue. The two men “agree to disagree” on accounts, he said. “But there is agreement on the goal of addressing Social Security solvency and trying to strengthen retirement security for most Americans.”

His personal lobbying credo of “maintaining good lines of communication with everyone” may ultimately strengthen the AARP’s hand in influencing a final outcome.

“People feel they can’t take AARP’s position for granted,” a senior vice president of the Alzheimer’s Association, Stephen McConnell, said. The Medicare precedent “suggests that he is going to look at the issue and decide on the merits,” Mr. McConnell said.

Mr. Rother maintains that solvency should be achieved by some combination of gradual benefits cuts and tax increases. He says some form of universal retirement savings accounts – which do not divert Social Security taxes – “are what we do need.”

“Half the jobs in America have no private pensions and people aren’t saving for the future,” he said.

Many advocates of private accounts oppose such “add-on” accounts because they do not increase the rate of return on Social Security contributions. Some Democrats worry that add-on accounts could become a back door to eventual “privatization,” but Mr. Rother’s allies say Democratic concerns are overblown.

“John is smart enough to know there is a good way and a bad way to structure [add-ons],” said Hans Riemer, the Washington director of Rock the Vote, a youth organization that has collaborated with AARP on Social Security polls and grassroots work.

“If they stay true to what they are saying, there is no reason to worry. They are doing more than anyone else to defeat privatization,” said Mr. Riemer, who has known Mr. Rother for 10 years and calls him an “inspirational figure” and a “center of gravity for the whole social welfare policy community.”

While the group will not detail its anti-accounts advocacy budget, in the first two weeks of January alone, it spent $5 million on newspaper ads.

The AARP does more than advertise and lobby politicians – the group “works through the public to influence lawmakers,” Mr. Rother said, by mobilizing citizens and encouraging them to give their representatives an earful.

Like the president, Mr. Rother has been touring the country promoting the group’s agenda. A recent tour took him to Washington state, Oregon, and Illinois.

Outside of the capital, he said, “People wonder why we can’t just solve these problems.”

“I think sooner or later Democrats will have to come forward with a plan,” he said.

With a white beard and St. Nicholas-like countenance, Mr. Rother speaks in gentle tones that bear little resemblance to the harshness of some of his group’s ads.

A native of Springfield, Mo., he grew up in Washington, D.C., the son of a Methodist chaplain at American University who turned his son on to politics through activism in the civil rights and anti-war movements.

“I wanted to end up in this world,” he said, sitting in a Senate room where he just finished speaking at a health policy panel.

After studying government at Oberlin College, a stint at divinity school, and earning a law degree from the University of Pennsylvania, Mr. Rother served for eight years as a special counsel on labor and health to Jacob Javits, a former Republican New York Senator. He later became the staff director and chief counsel for the Special Committee on Aging under its Republican chairman, Senator John Heinz of Pennsylvania – the late husband of Teresa Heinz Kerry.

In the Senate, Mr. Rother helped write legislation to promote pregnancy rights in the workplace, job safety, and labor law reform before joining the seniors’ group.

Despite working for two Republicans, Mr. Rother says he is a political independent.

His reputation around Washington is more as a policy wonk than a back-slapping lobbyist.

“John’s real strength is that he looks at these issues as policy questions, and does the analytic work in much more depth than most people. He is not the traditional lobbyist who goes to Capitol Hill and then swings influence around,” said Mr. McConnell, who has known Mr. Rother for 25 years.

A leading lobbyist on the other side of the issue, Derrick Max, who heads the pro-accounts Alliance for Worker Retirement Security, said he holds Mr. Rother in high personal regard.

“Considering the amount of respect I have for Rother, it’s disappointing to see him playing games,” said Mr. Max, referring to AARP’s dramatic ads. “The ads are not based in the reality of what is being discussed.”

Some critics suggest the AARP was pressured by Democratic allies to oppose the administration’s proposal as penance for supporting the prescription drug benefit.

Mr. Rother scoffs at the suggestion, saying the group first studied and rejected the idea of private accounts in the mid-1980s. “Our position has been constant for 20 years,” he said.

One proponent of accounts who has debated Mr. Rother, the Heritage Foundation’s David John, calls his sparring partner, “very good, very dedicated. He tends to make a good case, and is also very nice person.”

The secret of his success? “They are spending more money than anyone else,” Mr. John said.

Again, Mr. Rother begs to differ.

“That’s the answer they’d like to believe,” he said. “The real reason is that on questions of values, we are more in line with where the public is.”