Republicans and their allies are dusting off an old $500 billion deception about Medicare, trying once more to scare seniors into voting their way. The logic on this one turns truth on its head, but some in the media have caught on to this election tactic and have begun trying to supply missing context.

A bit of background: Before the 2010 mid-term elections, I wrote that both Democrats and the GOP had cynically exploited Medicare during the campaign, with Republicans ultimately winning that fight, not to mention the election. The Republicans hammered away at the argument—built on a half-truth—that the new health law would cut $500 billion out of Medicare, and they targeted members of Congress who supported the reform. Seniors carried the GOP to victory.

The facts were and still are these: The health reform law, aka the Affordable Care Act, does call for cutting $500 billion from Medicare to help finance subsidies for the uninsured. The administration portrayed these as “savings”—in other words, money not spent for Medicare that could be used for another purpose. But the important take-away is this: the law does not cut a dime from the basic Medicare benefits seniors receive. All seniors will still get hospital benefits, coverage for physician services, lab tests, hospital outpatient care, prescription drugs, and so on, and will continue to receive them unless pols on both sides of the aisle succeed in changing the fundamental structure of Medicare. (That indeed is possible after the election. But that’s for another post.)

Most of the $500 billion in cuts aim at reducing payments to health care providers—hospitals, nursing homes, home health agencies, though not doctors. And about one quarter of the cuts target Medicare Advantage Plans to reduce the amount of government overpayments insurers have gotten. The government was paying more to these plans to provide benefits than it was paying to provide the same benefits under the traditional Medicare program. Medicare Advantage plans are a popular alternative to traditional Medigap policies because those overpayments have allowed insurers to offer cheap premiums and extra benefits like dental and vision care. But policy experts found these payments were unwarranted, wasted money, and jeopardized the finances of the Medicare trust fund that pays for hospital care.

Of course, none of this is the stuff of campaign ads. That leaves the press to fill in the blanks.

A few news outlets are trying to do that. Tampa Bay Online reported that the US Chamber of Commerce has begun airing TV ads in some of the state’s largest cities attacking Florida Senator Bill Nelson, a Democrat who is up for reelection this year. Nelson’s sin, it seems, was supporting the Affordable Care Act. The Chamber’s ads include the “Republican contention that the plan cuts $500 billion from Medicare,” Tampa Bay Online noted. The website also points out that political fact-checking organizations, including the Annenberg Foundation’s FactCheck.org, have found that argument to be “false,” since the $500 billion figure “refers not to cuts but to limits on the planned increases in Medicare costs.” Do the findings of the fact-checking organizations make a difference in the electorate’s mind, or do the ads trump the facts? That’s something the media should explore as the campaign roars on.

The ads do grab attention, as in this smooth and reassuring message, aired by Jesse Kelly, a Republican running against Ron Barber for the House seat vacated by former Arizona Rep. Gabrielle Giffords: “Ron Barber wants to hide he supports Obamacare, which will cut $500 billion from Medicare. Our seniors deserve better.”

Jonathan Weisman over at The Caucus blog of The New York Times, also smoked out this year’s reincarnation of the $500 billion Medicare cut, reporting that the National Republican Congressional Committee sent out news releases targeting more than 90 Democrats running for Congress and “accusing them of slashing Medicare,” particularly Medicare Advantage plans. One aimed at Rep. Mark Critz, a Pennsylvania Democrat. The news released warned:

It should be remembered that the 865,000 Pennsylvania seniors that are on Medicare Advantage health plans will be particularly hard hit under his big-government law, since Critz’s government health takeover is paid for in part by nearly $200 billion in cuts to Medicare Advantage programs. Seniors currently on these plans could find their benefits at risk.

Trudy Lieberman is a fellow at the Center for Advancing Health and a longtime contributing editor to the Columbia Journalism Review. She is the lead writer for The Second Opinion, CJR’s healthcare desk, which is part of our United States Project on the coverage of politics and policy. Follow her on Twitter @Trudy_Lieberman.