Cutting federal health and retirement spending has long been at the top of the GOP agenda. But with Republicans in striking distance of winning the Senate, they are suddenly blasting the idea of trimming Social Security benefits.

The latest attack came in Georgia, where the National Republican Campaign Committee posted an ad last week accusing Rep. John Barrow (D) of “leaving Georgia seniors behind” by supporting “a plan that would raise the retirement age to 69 while cutting Social Security benefits.”

Crossroads GPS, the conservative nonprofit group founded by GOP strategist Karl Rove, has run similar ads against North Carolina Sen. Kay Hagan (D), Arkansas Sen. Mark Pryor (D) and Rep. Scott Peters (D-Calif.). Crossroads accused Hagan of supporting a “controversial plan” that “raises the retirement age.”

Pryor’s opponent, Rep. Tom Cotton, meanwhile, is one of at least three Republican candidates in competitive Senate races who have released cheery ads promising to protect Social Security. In Colorado, Rep. Cory Gardner (R) appears in a new ad with his “Grandma Betty” and vows to “honor every penny we promised today’s seniors” — a pledge that seems to conflict with demands by Republican congressional leaders for a less-generous inflation formula to calculate seniors’ cost-of-living increases.

Older voters typically dominate the electorate in non-presidential years, so the resort to Social Security as an issue in the Nov. 4 midterms is hardly surprising. But what has drawn attention – and charges of hypocrisy – is the decision by Republican groups to attack Democrats for supporting conservative ideas in a proposed “grand bargain” on the budget drafted by Democrat Erskine Bowles and former Republican senator Alan K. Simpson of Wyoming.

Once venerated in both parties as a good-faith proposal, the Bowles-Simpson plan calls for political compromise to rein in the $17.9 trillion national debt, which was dangerously elevated by the recent recession. Republicans would raise taxes, the theory goes, in exchange for Democrats cutting health and retirement spending. Among its proposals: trim Social Security benefits for well-off seniors, raise the retirement age to 69 by 2075 and adopt the new inflation measure, known as the chained Consumer Price Index, or chained CPI.

Both Crossroads GPS and NRCC, the party’s campaign arm for House races, have cited Democrats’ support for Bowles-Simpson as the basis of their charges on Social Security, though many Republicans — including Rove — have criticized President Obama for failing to support the Bowles-Simpson package.

A spokesman for Crossroads GPS declined to comment. NRCC spokesperson Andrea Bozek also declined to discuss the ad targeting Barrow, saying by e-mail only that “our ads are a comprehensive and accurate reflection of John Barrow’s record.”

Bowles and Simpson have responded with rebukes in local op-ed pages, most recently under the headline, “Barrow is brave.”

“We need members of Congress who have the guts to ignore these scare tactics and look at the substance of real solutions that will help get our great nation back on track,” the pair wrote in the Statesboro [Ga.] Herald in defense of Barrow, a moderate Democrat and five-term incumbent locked in a tight race with Republican businessman Rick Allen.

Reached by phone, Simpson declined to criticize the GOP groups. “How can you be disappointed?” he said. “It’s savagery out there.”

Former Republican senator Judd Gregg of New Hampshire, an original member of the 2010 debt-reduction commission led by Bowles and Simpson, was more direct.

“It really is inappropriate for Republicans to attack people who stand up for entitlement reforms, especially hard reforms to Social Security and Medicare along the lines of what Simpson-Bowles proposes,” said Gregg, who now serves as chairman of a debt-reduction organization called Fix the Debt.

But, he said, “In elections, you do whatever you think will work.”

There are obvious advantages to accusing one’s political opponent of monkeying with Social Security. A new survey out Thursday from the National Academy of Social Insurance found overwhelming support for the program among voters in both parties, with 69 percent of Republicans agreeing “it is critical to preserve Social Security benefits . . . even if it means increasing the Social Security taxes.”

More than 70 percent of Republicans and 92 percent of Democrats agreed that top earners should pay Social Security taxes on their entire earnings, not just wages under $117,700. Meanwhile, three-quarters of those surveyed oppose raising the retirement age and reducing cost-of-living increases, for example, by adopting the chained CPI.

Liberals are hailing the outpouring of Republican affection for Social Security, arguing that it reflects a broader consensus that government austerity is the wrong response to the sluggish economy.

“What gave Bowles-Simpson credibility was the fact that the president was after this grand bargain. Well, he is no longer trying to achieve a grand bargain,” said Roger Hickey, co-director of the liberal Campaign for America’s Future. “So now Bowles-Simpson is simply a way that politicians went on the record as being in favor of cutting Social Security and Medicare. And now it’s something that can be used against them.”

Bowles-Simpson supporters have a different take. They note that the ads have appeared in only a few races, and that the issue does not appear to be gaining traction. One exception is Louisiana, where the Democrat, Sen. Mary Landrieu, is attacking her Republican challenger, Rep. Bill Cassidy, for supporting an increase in the retirement age.

The ad targeting Peters, a freshman Democrat from San Diego, meanwhile, ran briefly and quickly disappeared.

“This is the most independent district in the country. It’s all about who is the true moderate, the true bipartisan consensus builder. And they made the case that it’s Scott,” said Peters campaign spokeswoman MaryAnne Pintar.

The fallout may be more apparent after the election. Maya MacGuineas, president of the bipartisan Committee for a Responsible Federal Budget, said prospects for a grand bargain on the order of the Bowles-Simpson plan are “in all likelihood dead” for the remainder of the Obama administration, but that hope remains for what she called “mini-bargains.”

Both parties, for example, are interested in easing scheduled agency cuts known as the sequester, which are due to hit again in 2016. Senate Republican Leader Mitch McConnell (Ky.), among others, has repeatedly held out chained-CPI as a possible replacement.

With a deadline on the debt limit looming again sometime next year, some Republicans have been quietly discussing the possibility of boosting Treasury borrowing power in exchange for adopting the new inflation measure, among other cuts to entitlement programs.

The campaign-season attacks run the risk of making either deal that much harder, MacGuineas said.

“Entitlement reform has always been the most difficult piece of the debt-reduction equation,” she said. “Attacking Democrats who have been willing to break with their party’s orthodoxy sets back the traditionally Republican agenda of entitlement reform tremendously.”