As the effort to reform health care nears the end, one of the biggest issues yet to be decided concerns the public insurance option.

Democratic leaders in Congress support creating a government-run health care plan that would be available to the uninsured.

But to get the plan past Republicans and conservative Democrats, they'll need to get a filibuster-proof 60 votes.

For his part, President Barack Obama says he supports the idea but does not want the health care overhaul to die because of it.

In recent days, leaders have huddled to come up with tweaks to the public option that would pass muster with the more conservative members of their caucus.

It's not yet clear which alternatives will survive or whether they'll push for the original proposal after all.

Here's the rundown:

THE PUBLIC INSURANCE OPTION:

The public option is a proposed government-run health insurance plan that would be available to uninsured Americans and serve as competition for private insurance companies. Proposals differ on exactly how the plan would be run and who would be eligible.

HISTORY:

Whether to include a public insurance option in Congress' health care overhaul has become the most polarizing issue in the debate going on in Congress right now.

Liberal Democrats in Congress have been calling for a government-run competitor to private health insurers for years. During the health care overhaul debate, supporters have labeled the idea a "public plan" that uninsured people would be able to enroll in, along with new plans offered by private insurers.

In the bills passed out of committee in the House (H.R. 3200) and by the Senate Health, Education, Labor and Pensions Committee (S. 1679), the public option is a federally run health insurer, with the rates it would pay doctors, hospitals and other health care providers negotiated by the government. A recently passed draft from the Senate Finance Committee did not include the public option.

But because of opposition by Republicans and some moderate Democrats, the public plan is changing.

Democratic leaders in the House and Senate are trying to find some sort of compromise that can get as many votes as possible. Under consideration are proposals that would give states a greater role in running the plan or leave it as a backup option in case other measures fail to reduce health care costs.

One option under consideration would let individual states “opt out” of the public plan. Basically, there would still be a federally run insurance option, but states could choose not to participate, or set up an alternative, if they wanted to.

A slightly different option — preferred by some centrist Democrats and Republicans — would be an "opt in." Instead of creating a big federally run insurance plan, individual states could set up their own plans with help from the federal government.

A third option under consideration is the "triggered" public option. After a number of years, if the other changes in the health care system that are part of the overhaul aren't successful in lowering insurance costs and covering people, the public option would go into effect.

So far, neither the House nor the Senate has decided which one to go with, or whether to combine the ideas somehow. Negotiations by Democratic leaders will decide what makes it into the bill that comes to the floor, giving lawmakers a chance to vote on it.

KEY SUPPORTERS:

President Barack Obama

Speaker Nancy Pelosi (D-Calif.)

Senate Majority Leader Harry Reid (D-Nev.)

Sen. Charles Schumer (D-N.Y.)

Rep. Henry Waxman (D-Calif.)

Former national Democratic Party Chairman Howard Dean

Families U.S.A.

Organized labor, including the Service Employees International Union and the AFL-CIO

ARGUMENTS IN FAVOR:

* A government plan would ensure competition. According to a Government Accountability Office report, a small number of insurance companies have a substantial share of the health insurance policies sold to small businesses in most states.

* A government plan could have lower premiums for individual consumers. That would force private insurers to keep their costs down in order to remain competitive.

* It would cover the uninsured. The government plan would ensure that a number of the estimated 46 million uninsured Americans have an option to get health coverage.

KEY OPPONENTS:

Senate Minority Leader Mitch McConnell (R-Ky.)

House Minority Leader John Boehner (R-Ohio)

Rep. Mike Ross (D-Ark.)

Rep. Earl Pomeroy (D-N.D.)

America's Health Insurance Plans, which represents private insurers

ARGUMENTS AGAINST:

* A government plan would have unfair advantages to negotiate prices. Eventually the public option would crowd out private insurance companies and lead to a government monopoly on health insurance or single-payer health care system.

* If the government negotiated to pay lower prices, doctors and hospitals would compensate by charging private insurance plans at higher rates. Experts say this "cost-shifting" already occurs with the government-run Medicare and Medicaid plans.

* It would cost too much. If the plan doesn't work as advertised, politicians would feel pressure to continue spending more in order to make it work. That would lead to higher and higher spending and even more unfair advantages over the private sector.

KEY VOTES:

None of the health care overhaul bills has come to a floor vote yet in the
House or Senate.

Drew Armstrong covers health care for Congressional Quarterly.