HELENA - As health care reform kicks into high gear in Washington, D.C., one of the fiercest political fights is over creating something called a "public option" insurance plan.

Yet few Americans even know what it is or how it's supposed to work.

"It's really striking to me that people focus on the political controversy, rather than the merits," said Jacob Hacker, a University of California-Berkeley political science professor and one of the authors of the idea.

What is the public-option plan?

Put simply, it would be a public health insurance plan launched, operated and sold by the government, for those without health insurance. People could buy the public plan, or, if they want, private health insurance.

It's assumed that most people who already have health insurance through their jobs would choose to keep it.

Those who don't - primarily the unemployed, the self-employed and employees of small businesses - may be required to buy health insurance, under reforms being considered by Congress.

The public option plan would be a choice for consumers, offering nonprofit competition to private health insurance, its supporters say.

"Right now, we don't have true competition," said Robert Struckman, spokesman for Montana Change That Works, a campaign financed by the Service Employees International Union (SEIU), which is a big backer of the public plan. "Having a public option will create a truly competitive insurance market."

Private health insurance companies and most Republicans, however, remain staunchly opposed to creation of the public-option plan.

They say it would be an unfair competitor that ends up shoving aside private insurance, and that other insurance market reforms being considered will make private insurance more affordable and able to cover everyone.

"We don't know that (the public plan) is necessary," said Frank Cote, senior director of government relations for Blue Cross/Blue Shield of Montana. "The other reforms to the private market seem to accomplish what the public plan sets out to do."

Late last week, President Barack Obama staked out his support for the public-option plan as part of a reform package. Most Democrats support it, too.

What would a public-option plan look like, and how would it work?

That depends on what Congress and the Obama administration decide, of course.

But supporters of the idea have written extensively about what should be included, and they spoke last week with the Gazette State Bureau about the details.

The public plan would not be bare-bones coverage, its supporters say. It would offer good, comprehensive coverage for doctor visits, hospital stays and preventive care, like most good private plans.

"The benefits have got to be real," said Alex Lawson, a health care research associate for the left-leaning Campaign for America's Future. "The public plan is not going to be some sort of high-deductible, catastrophic product. … And any sort of out-of-pocket costs are going to be subsidized, based on people's ability to pay."

For those with lower incomes, the price of the public insurance plan would be subsidized - and so would the prices for some private insurance plans, under proposed reforms.

One proposal says anyone earning between 150 percent and 300 percent of the federal poverty level would pay no more than 5 percent of their income for health insurance.

That income range is about $16,000 to $32,500 for a single person. Five percent of their income ranges from $800 to $1,600 a year.

Hacker, whose work on health policy influenced the health-reform positions of Obama and former Democratic presidential candidates in 2008, said the public plan could be designed to start as soon as next year.

It would be run by the U.S. Department of Health and Human Services and fashioned after the Medicare program, the government health-insurance program for the elderly, he said.

While Medicare has its problems and needs some changes, it remains extremely popular among consumers and has done a much better job than private insurance of controlling medical costs, Hacker said.

The public plan ideally would be financed by two sources: Premiums paid by those who buy into the plan and tax penalties paid by employers who choose not to offer health insurance to their workers.

Backers of a public-option plan also believe it can be a force for controlling costs and improving health-care practices, by its stature as a new, nonprofit competitor with a national reach.

A public plan will have more motivation to provide preventive care, can lead the way on innovative payments that reward physicians and hospitals that contain costs - and will make public its methods for reducing costs, Hacker said.

"My vision is that the private plans that are most innovative will be able to compete" with the public plan, he said. "The argument is that we need to have a benchmark that is high, so the private companies are not just making their money through consolidation and monopolistic practices, or by just selecting healthy people to insure.

"There really needs to be an effective check on private (insurers). To let them compete among another is not enough."