The U.S. Supreme Court is expected to rule this week on the fate of the Affordable Care Act, the sweeping 2010 health care reform law also known informally as “Obamacare.”

Rarely have so many Mainers been waiting for the justices to make a decision.

“It’s a big unknown hanging out there, and I think a little certainty would be welcome,” said Doug Newman, who owns Newman Concrete Services in Richmond.

Newman is one of many business owners who hope the law gets struck down before costly mandates take effect in 2014.

Other Mainers, such as Joy Drew, of Scarborough, hope the law survives because of the way it already is expanding access to health insurance.

“Everybody needs insurance,” said Drew, who will be waiting for the court decision in Boston, where her 25-year-old daughter is recovering from a double lung transplant.

Because the law is so large and complex, the ruling could touch virtually everyone who has health insurance, as well as everyone who doesn’t.

Maine insurance carriers, employers and health care consumers are waiting to see if the law survives. Gov. Paul LePage and state lawmakers are watching, too, because the ruling — whatever it is — probably will prompt legislative responses in Augusta and in Washington.

Insurance companies in Maine and around the country have pledged to maintain some health care benefits introduced by the law — including coverage of adult children — regardless of the Supreme Court’s decision. Others say they will re-evaluate when the dust settles.

Maine is one of 26 states that sued to overturn a core provision in the law — a requirement that all Americans buy health insurance beginning in 2014. Under the law, consumers who can’t afford insurance could apply for new subsidies.

Critics say the so-called individual mandate is unconstitutional because the government can’t force citizens to buy a product or service. Defenders say the mandate simply requires people to pay for the care they inevitably will need. They argue that medical care for the uninsured is now paid for through higher insurance premiums on those who are insured.

The Supreme Court could uphold the law, kill it or strike down part of it. Eliminating just the individual mandate could cause other parts of the complex law to unravel.

Doug Newman said he’s confident that the law won’t survive. While Newman doesn’t like the individual mandate, he said a different requirement would hurt his business more.

Starting in 2014, employers with 50 or more workers would have to provide health insurance to their workers or pay a $2,000 penalty for each one to help cover the cost of private insurance. Newman has 55 employees and already provides health insurance for established workers. Under the law, he would have to provide higher-cost health plans and would have to cover even short-term employees, he said.

“If this gets struck down, I think you’re going to hear a sigh of relief from business owners around the country,” said Newman, whose wife, Kathleen Newman, is the legislative director for LePage.

Many in Maine’s tourism industry also hope the law will be struck down, or at least changed. That’s because employers would have to provide health insurance to seasonal employees who work at least 120 days a year.

Greg Dugal, director of the Maine Innkeepers Association, said some inns and hotels would have to make sure they hire fewer than 50 workers or they would have to shut down for a month or two to keep them from working 120 days.

“Most everybody is open five or six months to make a go of it,” Dugal said. “People are … going to have to sacrifice part of their season so they don’t have to provide health insurance (that they can’t afford). … They’ll have to choose between May and October.”

Opinions in the industry are mixed about the law overall, Dugal said, although innkeepers agree that the time limit for seasonal workers has to be longer.

Many Mainers are watching and hoping that the court will uphold the law. In fact, while the most controversial provisions of the law won’t kick in until 2014, more popular provisions already have taken effect.

Last week, for example, federal officials announced that 10,589 Mainers will be paid health insurance rebates — an average of $468 each — because of new limits on the industry’s administrative expenses.

Joy Drew’s daughter, Ashley Drew, has become a poster child for one of the law’s most popular provisions: a requirement that insurance plans cover dependent children until they turn 26.

Before the passage of the Affordable Care Act, plans in Maine covered children until age 25 under certain conditions.

Ashley Drew was born with cystic fibrosis, a genetic condition that leads to life-threatening lung infections. She ran track and played the flute in high school, but her condition got dramatically worse while she was at the University of Maine, studying to become a music teacher. She was hospitalized repeatedly and put on a waiting list for a double lung transplant.

In August, while waiting for the transplant, Drew turned 25.

Only because of the Affordable Care Act could she stay on her mother’s health insurance to cover most of the cost of the expensive life-saving surgery, Joy Drew said.

On June 8, after 540 days on the waiting list, Ashley Drew got her new lungs. She’s now recovering at Brigham and Women’s Hospital in Boston.

“She’s doing great. The lungs are doing great,” Joy Drew said.

Ashley Drew and her family are big fans of the law and the expanded access to health insurance. “At some point in your life, you’re going to need it,” Joy Drew said.

Ashley Drew now hopes to stay on her mother’s insurance plan until she turns 26.

Things are uncertain after that. Her family hopes the law will survive the court challenge and help her get her own coverage despite her pre-existing condition.

Coverage of adult children is one provision that probably will survive, even if the law does not.

Three health insurance carriers in Maine — Aetna, Harvard Pilgrim Health Care and UnitedHealth Group — have said they plan to maintain coverage of dependent children until they turn 26, no matter what the court rules.

They also plan to continue providing 100 percent coverage of preventive care, another provision of the law that’s already in effect. The two provisions have added minimal costs to health insurance premiums in Maine, industry experts say.

“We believe that a number of the provisions in the health reform law are really part of the fabric of our health care system and they bring real value to customers and consumers and should be maintained,” said Susan Millerick, spokeswoman for Aetna, which has about 145,000 members in Maine.

Representatives of Cigna Corp. and Anthem Blue Cross and Blue Shield of Maine, the state’s largest carrier, said they will wait until after the Supreme Court rules to discuss their plans regarding the law.

“I think each health plan is handling that in their own way,” said Katherine Pelletreau, executive director of the Maine Association of Health Plans, which represents the carriers.

Pelletreau said all of the insurance companies will continue to follow the law and keep a close eye on the Supreme Court. “Until we hear otherwise, the Affordable Care Act is the law of the land.”