“Did you know with your health insurance, you may now have some preventive benefits with no co-pays or out-of-pocket costs?” one asks.

Here in the suburbs of Philadelphia, which, according to the Campaign Media Analysis Group, is one of the top five media markets for ad spending against the health care law, it is apparent how such messaging is playing out. (The other top markets are Orlando, Fla.; Tampa, Fla.; Pittsburgh; and Denver, all in swing states.) In interviews with about two dozen residents who were mostly opposed to the law, certain worries, resentments and dark predictions about it came up time and again.

Nearly everyone said the nation could not afford the law’s goal of insuring about 30 million Americans, mostly through a vast expansion of the Medicaid program and federal subsidies to help others who cannot afford to buy coverage on their own. A striking number of people also said the law would limit patient choices and lead to rationing of care — a fear that has been stoked by conservative lawmakers, talk-radio hosts and commentators on networks like Fox, in addition to the political action committees that have run ads attacking the law.

In Doylestown, Richard Tems, a businessman and member of the Bucks County Republican Committee, echoed the national messaging against the law as he ticked off reasons it was a bad idea. Mr. Tems, 64, said the hip replacement surgery he had three years ago might not have been possible under the law, which he believes will lead to rationing and, ultimately, a system of socialized medicine.

“I got to pick my surgeon, I got to pick my hospital, I got to pick the day I was getting it, I got to pick the kind of hip I wanted,” he said. “All of that goes away. If you look at any nationalized health program, whether it’s Canada’s or England’s, they ration everything.”