Timed to hit the airwaves just before the Republican National Convention, scheduled to begin on Monday in Tampa, the ad will be shown only in several key "battleground" states, including Ohio, said an Obama campaign official who discussed the ad before its release only on condition of anonymity.
"The purpose of this particular ad is to draw a sharp contrast between two competing visions of economic security for the middle class," the campaign spokesman said.
The ad opens with a still photo of President Obama leaning in as he meets an older woman, followed by a still photo of President Lyndon B. Johnson signing the Medicare bill in 1965 with former President Harry Truman at his side.
"It's a promise that was made long ago," the announcer says.
Each line spoken by the announcer is accompanied by a video snippet, the message reinforced by words across the screen.
"You work hard," the announcer says, and the visual is of a man shelving groceries.
"Pay in," he says, and a middle-aged woman looks through papers at her desk, a family photo in the background.
"Your Medicare benefits are guaranteed," he says, and a woman in a white coat and a man in medical scrubs speak to a gowned man seated on an examining table.
"But Mitt Romney would break that promise. Replace your benefits with a voucher," he says, and as the scene shifts to Mitt Romney and Paul Ryan waving to a crowd of sign-carrying supporters. Then a worried-looking older man looks at the camera, and the announcer says, "Replace your benefits with a voucher."
The words on the screen attribute that to a November, 2011, Associated Press story about the Medicare plan Mr. Ryan, a Wisconsin Republican, introduced in the House of Representatives.
"Insurance companies could just keep raising rates," the announcer says, with words on the screen attributing that to a Boston Globe editorial, and another older man tosses papers and a receipt among the calculator and coffee cup on his kitchen table.
"Instead of a guarantee, seniors could pay $6,400 more a year," the announcer says, and an older woman is shown at a table with medicine bottles, parceling out her pills for the week ahead. That statement is attributed to the Center on Budget and Policy Priorities.
"AARP says the plan Mitt Romney supports undermines Medicare," he says, as an older woman sits on a doctor's examining table, her head bowed, her hands clasped.
The ad closes with a still photo of Mr. Romney, brow furrowed and lips pursed, as the announcer says, "Mitt Romney. An end to the Medicare promise."
The President's name is only heard at the beginning, with the standard candidate voice-over saying he approved the message, and at the end, in small print, "Approved by Barack Obama. Paid for by Obama for America."
The purpose is "to make sure that senior citizens in Ohio understand the differences between the two candidates," the Obama campaign spokesman said.
"The President is committed to strengthening Medicare. There would be a very different plan for the future of health care under a Romney-Ryan presidency."
Jon Stainbrook, chairman of the Lucas County Republican Party, said the Obama campaign is only airing such an ad before the convention because the President and his challenger are neck-and-neck in the polls.
"The timing speaks for itself," Mr. Stainbrook said. "The Barack Obama campaign wants to frighten senior citizens. To me, the campaign doing this is deplorable. It's a desperate attempt to frighten a group of people who should be held in the highest esteem."
He said the President's campaign, in trying to shore up support among senior citizens, "brings in falsehoods and wants to imply things, like those vouchers would hurt seniors, and it's just not the case."