The overwhelming majority of the population would remain in private health insurance plans sponsored by employers. Others, mainly low-income people, would be covered through an expanded Medicaid program.

To be fair, most people would not have access to the new public plan. Under the House bill, it would be offered through new insurance exchanges open only to those who buy coverage on their own or work for small companies. Yet even within that pool of 30 million people, only 1-in-5 would take the public option.

Who's likely to sign up?

The budget office said "a less healthy pool of enrollees" would probably be attracted to the public option, drawn by the prospect of looser rules on access ...

The overwhelming majority of the population would remain in private health insurance plans sponsored by employers. Others, mainly low-income people, would be covered through an expanded Medicaid program.

To be fair, most people would not have access to the new public plan. Under the House bill, it would be offered through new insurance exchanges open only to those who buy coverage on their own or work for small companies. Yet even within that pool of 30 million people, only 1-in-5 would take the public option.

Who's likely to sign up?

The budget office said "a less healthy pool of enrollees" would probably be attracted to the public option, drawn by the prospect of looser rules on access to specialists and medical services.

As a result, premiums in the public plan would be higher than the average for private plans. That could nudge healthy middle-class workers and their families to sign up for private plans.

"The concern was that the public option would destabilize the bulk of private insurance, but in fact what Congress has fashioned is very targeted," said economist Karen Davis, president of the Commonwealth Fund. "It's not going to be taking away the insurance industry's core business."

It's unclear whether there are enough votes in the Senate for a public plan. The version that Majority Leader Harry Reid, D-Nev., has offered would let states opt out, probably leaving a smaller plan that the House would want.

Insurers aren't buying the budget office analysis. Asked if it might soften that opposition, industry spokesman Robert Zirkelbach of America's Health Insurance Plans responded with a curt "No."

While a government plan might start out modestly, insurers fear that Congress could change the rules later, opening it up to all people and setting take-it-or-leave payments for hospitals and medical providers, instead of negotiating, as the House bill calls for.

For the same reason, employer groups also remain wary. Big companies don't want to lose control o