WASHINGTON — Courting one of the nation’s largest voting blocs, Senator Clinton told AARP members here yesterday that she was prepared to fight for expanded health coverage and resist attempts to “privatize” Social Security.

Mrs. Clinton addressed the group’s annual public policy meeting, delivering a low-key but detailed talk in which she touched on a range of health- and retirement-related issues at the top of AARP’s agenda.

While she made little reference to her presidential campaign and offered no new policy proposals, the intent of her appearance was clear: With nearly 38 million members 50 years or older, AARP — formerly the American Association of Retired Persons — represents a powerful and expanding constituency, and one that accounted for 25% of all voters in 2006, according to its estimates.

Mrs. Clinton also had the powerful stage largely to herself — no other 2008 hopeful accepted the group’s invitation to address its conference this week.

As she has done repeatedly since launching her White House bid last month, Mrs. Clinton acknowledged her unsuccessful effort as first lady to overhaul the nation’s health care system. The circumstances are different this time around, she said, and unlike in the 1990s, “pressure for change” is coming from the private sector as well as political leaders.

“I actually think the stars may be more in alignment today than they have been,” she said, speaking without notes to a group of several dozen people.

AARP does not endorse candidates, but its support for expanded public health care and its opposition to President Bush’s plan for private accounts for Social Security are closer to Democratic positions.

Mrs. Clinton said she was proud of the Democrats’ “very strong stand against the privatization of Social Security,” and she warned that the threat had not dissipated, noting that the president included funding for a private account program in his 2008 budget. The Bush administration has not made private accounts a priority since its aggressive push for Mr. Bush’s plan failed to win over Congress in 2005. “It’s like the bad dream that doesn’t disappear,” Mrs. Clinton said.

A survey that AARP conducted last year of 1,000 of its members found a mixed political bag. Thirty-five percent identified themselves as Democrats, 32% as independents, and 27% as Republicans. But far more members, 37%, identified as conservative than liberal, 14%, while more than two out of five said they were moderate.

A spokeswoman for the group, Cecelia Prewett, said officials had invited all of the presidential candidates from both parties to speak at their three-day meeting, which began yesterday, but only Mrs. Clinton has said yes thus far. Ms. Prewett said AARP would continue to reach out to the candidates throughout the campaign.

Older Americans vote far more regularly than younger citizens, and 90% of AARP members say they are registered to vote, according to the group’s surveys.

The statistics add to AARP’s status as an influential lobbyist, and with the aging of the baby boom generation, its ranks are growing.

“What it tells us is that political leaders have to pay attention to the issues that matter to older voters and their families,” Ms. Prewett said.

Mrs. Clinton should be at an advantage among aging voters in the Democratic primary. At 59, she is several years older than the party’s other top early contenders, John Edwards, 53, and Senator Obama, 45. And emphasizing her experience over eight years in the White House and six in the Senate could resonate more with an older population.