At the same time, Medicaid would be expanded greatly to cover millions more low-income people, childless adults who do not now qualify.
Between the two approaches, more than 30 million uninsured people are expected to obtain coverage. Millions more will gain the security of knowing they can't be turned down for health insurance if they switch jobs.
That's critical for Natalie Hough, a college sophomore from Hillsborough, N.C. An aspiring artist, Hough has a heart condition that probably would make her uninsurable if she had to apply on her own later in life. Starting in 2014, insurers will not be able to turn away people like her.
"It's definitely peace of mind, knowing that I can go to a hospital if I need to," she said. "I'm an art major, and I'm not going to make billions of dollars."
But such changes hinge on whether the law's requirement that most people have health insurance is upheld by the Supreme Court.
This individual mandate, the main target for the law's critics, also takes effect in 2014. Without it, many experts fear that the new exchanges, the state-based markets for private insurance, won't work. Healthy people would be tempted to postpone signing up until they get sick, raising costs for everybody.
Administration lawyers have advised the court that if it strikes down the mandate, it also should invalidate the requirement that private health insurers accept customers with health problems.
If the court leaves the rest of the law in place, the Medicaid expansion could continue.
But even if Obama's plan to expand coverage survives its test of constitutionality, expect the law's cost-control measures to remain under attack.
One is an independent board that would have the power to curb excessive increases in Medicare spending by ordering cuts if Congress fails to act first. Republicans call it a "rationing board," although the law specifically bars the yet-to-be-named panel from restricting access. The health care industry opposes the board; efforts to do away with it or diminish its role seem to be gaining ground.
"It would work like a random tax on medical innovation," said economist Douglas Holtz-Eakin, a Republican adviser. "If you were an innovator, why would you want to bring something new to market when the biggest payer in the country is periodically lopping off spending?"
The other main cost-control measure is a tax on generous health insurance plans. Labor unions oppose it.
It won't take effect until 2018, a year after a second Obama term would have ended.
Health care law: http://www.healthcare.gov/
Supreme Court: http://tinyurl.com/3zukoc4
Copyright 2012 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.