Insurance companies argue that if only the sick sign up, insurers will go broke. So the law says everybody must have insurance for themselves and their children, or pay a penalty.
Also, because everyone needs health care sometime, if everyone purchases insurance, the price per person can be lower, with the cost of care spread out over many people.
After all, the government requires workers to pay Social Security and Medicare taxes, whether they want the benefits or not.
One argument for the insurance mandate is that the fines are just federal taxes by another name. Another is that it falls under the government's constitutional power to regulate commerce that crosses state borders.
State governments, of course, tell people to buy lots of things, including auto insurance or motorcycle helmets.
"You can always move to another state," said Tom O'Connor, a consultant in Fairfax, Va., who thinks the health care law overreaches. "It's a little more difficult to move to another country."
In an Associated Press-GfK poll, 85 percent said the U.S. government should not have the power to require people to buy health insurance. When the question is worded without the specific reference to federal power, acceptance of the mandate grows a bit, but 6 in 10 are still against it.
Even among those who generally support the health care overhaul, one-third said they are against the insurance mandate.
There's also a significant minority who sees mandates as a cop-out and prefer a government program that covers everyone, Medicare for all.
It's clear that many people do not understand what the law would do or how it would affect them.
Jan Gonzales, an out-of-work bookkeeper in Pablo, Mont., calls fining people for going without insurance "the most ridiculous, asinine thing you ever heard of."
"If I can't put food on the table for my children, how can I pay for health care coverage?" asks Gonzales, who's been without insurance for seven years. "What moron came up with that idea?"
Of course, she might qualify for the law's exemptions for those too poor to pay and for assistance for low-income people, as well as many in the middle class.
There also are some religious exemptions. .
Estimates vary widely of how many uninsured people will get insurance once it's required in January 2014.
About 4 million people would pay a penalty to the Internal Revenue Service for being uninsured in 2016, the Congressional Budget Office estimates.
By 2016, the fine reaches $695 per uninsured adult or 2.5 percent of family income, up to $12,500 per year. The IRS is in charge of the penalties but can't prosecute violators or place liens against them. Its only enforcement option may be withholding money from refunds.
That leaves insurance companies, who stand to gain lots of new customers, worried that people instead will shrug off the weak mandate.
Meanwhile, the state-federal Medicaid program will expand to cover more low-income people, and that's another issue before the Supreme Court, because many states say they cannot afford the extra cost.
Health care law: http://www.healthcare.gov
Supreme Court: http://www.supremecourt.gov/docket/PPAACA.aspx
Associated Press writer Stacy A. Anderson contributed to this report.
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