"If someone has a heart attack," Romney said, "they don't sit in their apartment and die. We pick them up in an ambulance, and take them to the hospital, and give them care. And different states have different ways of providing for that care."
But on television two years ago, Romney said the use of emergency rooms for routine healthcare a problem.
The so-called free-rider problem was one rationale behind Massachusetts's healthcare reform law, which went into effect when Romney was serving as governor there and inspired the nationwide Affordable Care Act.
"It doesn't make a lot of sense for us to have millions and millions of people who have no health insurance and yet who can go to the emergency room and get entirely free care for which they have no responsibility, particularly if they are people who have sufficient means to pay their own way," Romney said in 2010.
Care in the emergency room is among the most expensive, and in many cases, hospitals never recoup its full cost.
On Sunday, Romney seemed to invoke the idea of ER care to make a point about federalism and head off associations between his Massachusetts law and the federal healthcare overhaul.
Some states give the uninsured care "through clinics," Romney said. "Some provide the care through emergency rooms. In my state, we found a solution that worked for my state.
"But I wouldn’t take what we did in Massachusetts and say to Texas, 'You’ve got to take the Massachusetts model,' " he added.
Romney's campaign responded to the Obama Web video by criticizing the Affordable Care Act as a "costly disaster" and promising "commen-sense, patient-centered" healthcare reforms under a President Romney.
In a statement, campaign spokeswoman Amanda Henneberg also defended Romney's comments on emergency-room care.
"Governor Romney made a statement of fact, that Americans without health insurance are still able to receive critical care, including in some cases through emergency rooms," Henneberg said. "It is an absurd misreading of his comments to imply that he offered emergency rooms as a 'solution' to our nation’s healthcare challenges."
—This post was updated at 11:17 a.m.