Mitt Romney may know more about healthcare than any other presidential nominee in memory. As governor of Massachusetts, he dove deeply into the subject while creating the most far-reaching state health plan in the country. As president, he would bring an unusual degree of nuance to any discussion of health insurance.

In theory, that should thrill Republicans, who have been eager to run against an incumbent who unwittingly gave his name to a healthcare plan, “Obamacare,” that has engendered more opposition than support.

So why has explaining his position on healthcare been such an ordeal for Romney?

He may have made some headway in the first presidential debate, despite some misstatements of facts. As he has throughout his campaign, he promised that, if elected, he would repeal and replace Obamacare. However, he has rarely spoken specifically about how he would replace it, and until recently rarely talked about his signature accomplishment in Massachusetts — the health plan that came to serve as a model for President Obama’s Patient Protection and Affordable Care Act.

He also, over the course of the campaign, has come out with statements about healthcare that have left even some ardent supporters scratching their heads.

On a trip to Jerusalem this summer, he praised Israel for providing good healthcare while keeping costs lower than in the United States. He did not mention that those achievements were the fruit of a nationalized healthcare system of the sort that Romney, along with most Americans, adamantly opposes.

Asked on CBS’ “60 Minutes” what he would do about Americans who lack health insurance, Romney replied that the country already had a system in place for them: emergency rooms. “We pick them up in an ambulance and take them to the hospital and give them care,” he said.

That answer flew in the face of universally accepted wisdom that ERs are the most expensive places to provide routine care, and also contradicted Romney’s own statements. Two years ago, he said in another televised interview: “Look, 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.”

Either of those might be dismissed as slips of the tongue, or perhaps defended as statements of fact that Romney didn’t intend as road maps of policy. What has been more difficult for Romney has been crafting a message about Obamacare that doesn’t implicitly disavow his own plan in Massachusetts, which has inevitably come to be known as Romneycare.

“I think in his heart, he thinks he did a good job in Massachusetts,” said Michael D. Tanner, a senior fellow with the libertarian-leaning Cato Institute who specializes in healthcare. “And he doesn’t want to say anything about it, and he hasn’t really sat down and studied anything else because he doesn’t see the need for an alternative.”

Romney has, in fact, proposed alternatives, and has won praise for them in some conservative circles (along with complaints that he hasn’t been sufficiently specific). He proposes a system in which consumers would have “portable” insurance plans, subsidized through tax deductions, that they could take from job to job. He also would partially privatize Medicare, the government health plan for seniors and disabled people (but only for future recipients), and would give states flexibility about how they spend on Medicaid, the program for the poor.

As with Obamacare, he says he would require insurance companies to accept customers with preexisting medical conditions. Unlike Obamacare, however, he would limit this to people who have been continuously covered by insurance — a detail he sometimes drops, including in the first debate. It is not clear what would happen to uninsured patients with preexisting conditions.

At the same time, after months of barely mentioning his Massachusetts plan, he has begun to tout it and has even embraced the idea that it served as a model for Obamacare.

In a candidates’ forum with the Spanish-language network Univision, he said: “The president says I’m the grandfather of Obamacare. I don’t think he meant that as a compliment, but I’ll take it.”

In the debate with Obama, he also accepted full paternity of the Massachusetts plan, not so much for its impact on healthcare as for what it said about his ability to reach across the aisle and craft bipartisan legislation. This is a significant aspect of his career that has loomed larger as the Republican primary campaign has receded farther in the rearview mirror.

“I like the way we did it in Massachusetts,” he said. “I like the fact that in my state, we had Republicans and Democrats come together and work together.” By contrast, he said, Obama rammed his healthcare plan through Congress without Republican support.

In the debate, Romney repeated several erroneous claims he has made during the campaign, among them the oft-debunked claim that the law includes a new government board that is “going to tell people ultimately what kind of treatments they can have.”

His criticism of Obamacare rests on the idea that it is an overreach by the federal government — a “risky federal takeover of healthcare” — into policies best enacted by states. It’s a nuanced argument that may be lost on voters who reason that what’s good for a state should also be good for the country. And in substance, Obamacare and Romneycare are quite similar.

“They’re not identical twins, but they’re probably fraternal twins,” said Henry Aaron, a healthcare analyst at the Brookings Institution.

The Romney plan was the first in the country to rely on the device known as an individual mandate, requiring virtually everyone to buy health insurance or face a fine. The system relies on this logic: Only when everyone jumps into the insurance pool, including the healthiest people, is it possible to afford coverage for the sickest people, including those with preexisting conditions.

Although accounts differ as to who first came up with the idea, the mandate was prominently pushed by the conservative Heritage Foundation in the 1990s as a free-market alternative to socialized medicine. By the time Romney crafted the Massachusetts plan, it was beginning to win support on both sides of the aisle as a practical way to bridge the ideological divide and accomplish universal coverage.

It has long since lost support among conservative healthcare wonks, including those at Heritage, replaced with something much closer to what Romney now proposes.

“I think what Gov. Romney is articulating is different from what is described in Massachusetts,” said Nina Owcharenko, director of the Center for Health Policy Studies at the Heritage Foundation. While demurring that Romneycare is “a mixed bag,” she said there was no point in comparing it to Romney’s national plan: “It’s an apples-and-oranges comparison.”

mitchell.landsberg@latimes.com