But Thompson wasn’t alone. Rep. Rick Berg, running for the Senate in a closer-than-expected race in North Dakota, became the latest in a string of Republican candidates to say they disagreed with Romney’s 47 percent remarks.

Apart from his self-inflicted political wounds, Romney has been under pressure from fellow Republicans to draw clearer distinctions with Obama on the economy, and say more clearly what he would do to bring down the nation’s 8.1 percent unemployment rate.

Asked to point to new policy proposals that Romney has made since early August, aides referred to one speech on energy independence and a set of remarks on veterans.

But he has generally been unwilling to flesh out his plans for balancing the budget or enacting tax reform, refusing, for example, to name a tax break he would eliminate except for a small one that subsidizes producers of wind power.

He criticized Obama’s handling of anti-American demonstrations around U.S. embassies in the Middle East earlier in the month, but declined to say what approach he would have taken instead. And while he has repeatedly tagged Obama for not being more forceful in trying to arrange the downfall of Syrian President Bashar Assad, aides have refused for nearly a month to say whether the Republican challenger supports arming rebels fighting the regime.

Ryan provided no new policy details in his appearance before the AARP, although he renewed Romney’s support for a gradual increase in the Social Security retirement age and slowing the growth of benefits for those at higher incomes. Republicans have yet to provide details.

He told seniors that Republicans ‘‘respect you enough to level with you,’’ and said Obama’s health care legislation had cut $716 billion out of Medicare over a decade and set up a board of unelected bureaucrats with authority to make future reductions so severe they could eventually jeopardize seniors’ access to medical care.

‘‘You know President Obama’s slogan, right? Forward.’’ he said, then added, mockingly, ‘‘Forward into a future where seniors are denied the care they earned because a bureaucrat decided it wasn’t worth the money.’’

Obama answered via video hookup and a television commercial that began airing in Florida, Colorado and Iowa. It argued that under the Republican plan, seniors’ health costs could go up by $6,400 a year.

Obama has said he would consider raising payroll taxes on upper-income wage earners to shore up the trust fund that pays for Social Security benefits. Workers currently pay a 4.2 percent tax on income up to $110,100 annually, although the rate is scheduled to revert to a previous 6.2 percent at the first of the year.

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