WASHINGTON – The second sign-up season under President Barack Obama’s health overhaul opened Saturday, with hopes that this time consumers will have a positive experience.

But the fear is that entrenched political opposition and renewed legal challenges may yet collapse the program that’s bringing health care to millions of previously uninsured Americans. The administration can’t afford another technology meltdown.

With 7 million paying customers in new insurance markets, the Affordable Care Act has shown it is helping to reduce the number of uninsured. Insurers, not known for altruism, have stuck with the fledgling program despite ongoing technical headaches with the HealthCare.gov website. More companies are participating for 2015, a sign they see a business opportunity.

Obama urged consumers, whether they currently buy coverage through the insurance markets or still need to sign up for a plan, to go to the health care website and review their options. He said they could end up saving money or finding a better plan, and urged them to act fast since the enrollment period closes Feb. 15.

“This window won’t stay open forever. You only have three months to shop for plans, so it’s worth starting right away. And it might make a big difference for your family’s bottom line,” Obama said Saturday in his weekly radio and Internet address, which the White House released as the president visited Brisbane, Australia.

The administration said late Friday that some HealthCare.gov functions would be turned off for several hours in the transition to the start of sign-up season. The website appeared to functioning early Saturday.

“Obamacare” is still struggling to win hearts and minds. The latest Associated Press-GfK poll finds that, if forced to choose between repealing the law and implementing it as written, 56 percent of Americans would repeal it completely. Only 41 percent would carry it out.

However, most don’t see the law going away. Sixty-one percent said they expect it to be implemented in its current form, or something near that.

Health and Human Services Secretary Sylvia M. Burwell, a management expert assigned to save what’s been a problem child of social programs, says she’s confident the sign-up season will be successful, even if it’s only half as long as last year’s: three months, through Feb. 15.

Will the law remain on the books after Republicans gain full control of Congress in January?

“The idea of repeal ... is not something this administration will let happen,” said Burwell.

What about the legal challenge the Supreme Court has just agreed to hear, calling into question the law’s tax credits that make premiums affordable for millions?

“Nothing has changed,” Burwell said, adding that the tax credits “will be continuing.” At least for the time being. The Supreme Court isn’t likely to hear the case until the spring, after 2015 open enrollment is over.

Website outages are not out of the question this year, but a full-scale meltdown seems less likely. HealthCare.gov has been revamped to handle last season’s peak loads and beyond. The federal website will serve as the online portal for coverage in 37 states, while the remaining states run their own insurance exchanges. Consumers can also apply in person or through call centers.

The pool of potential customers is an estimated 23 million to 27 million people who don’t have access to affordable coverage on the job.

For most newcomers, the online application has been simplified, cut to 16 computer screens from 76. Navigation is easier. Window shopping is available without first having to create an account.

Premiums for 2015 are a wild card. Nationally, the average increase is expected to be modest. But prices can vary dramatically from state to state, even within regions of a state. Many returning customers could end up facing premium increases if they don’t shop around.

The administration is seeking to lower expectations. Burwell said her target is a total enrollment of 9.1 million people in 2015, a 28 percent increase. The nonpartisan Congressional Budget Office had estimated the number would nearly double, to 13 million people enrolled next year.

The administration is facing several new tests.

This sign-up period will be the first time that renewal has been tried for current customers, and also overlaps for the first time with tax-filing season.

For those already signed up, coverage will renew automatically if they do nothing, but that may not produce the best result. The returning customers could miss out on lower-premium options and get stuck with outdated and possibly incorrect subsidies. In most cases, they have until Dec. 15 to update their income information or switch insurance plans, in order to have the changes take effect on Jan. 1.

The tax issues will emerge during next year’s filing season.

Current customers who got tax credits this year will have to file new tax forms to prove they got the right amount. Too much subsidy and their tax refunds will be reduced. Too little, and the government will pay them.

People who remained uninsured risk a penalty that will be deducted from their tax refunds. Millions may qualify for waivers, but getting exemptions could involve a paperwork ordeal.

Community-based counselors helping uninsured people say interest remains strong, but they worry about this year’s abbreviated sign-up season.

Nathalie Milias, who works with Haitian groups in Miami, said she has been feeling the demand since the summer as uninsured people approached her.

“They see me in the store, they call,” said Milias. “The locations I go to are already calling and saying, ‘How many appointments do you want for Monday?’”

Associated Press writer Kelli Kennedy in Miami contributed to this report.

What’s covered, what’s not in health overhaul

SACRAMENTO, Calif. – As the federal government and states launch a second round of enrollment under the health care law, consumers should be aware of what’s covered and what’s not when buying health coverage through insurance marketplaces. Plans cover essential health benefits, pre-existing conditions and preventive care, but dental and vision benefits vary.

Here are some questions and answers about individual coverage:

Q: How do I choose the right plan?

A: Just like last year, there are five categories or metal levels of coverage including bronze, silver, gold, platinum and catastrophic. Plans in each category pay different amounts of the total costs of an average person’s care. For a silver plan, your health plan will pay an average of 70 percent, you pay about 30 percent.

If you expect a lot of doctor visits or need regular prescriptions, you may want a gold or platinum plan that have higher monthly premiums but pay more of your costs when you need care.

If you don’t expect to use a lot of medical services, you may want a silver, bronze, or catastrophic plan that cost you less per month, but pay less of your costs when you need care.

Catastrophic coverage is available only to people who are under 30 years old or have a hardship exemption.

Q: Is vision coverage available?

A: Health plans don’t have to include adult vision coverage, only pediatric vision coverage. If your plan doesn’t include adult vision coverage, you can buy stand-alone plans for an additional cost outside the exchange.

Insurers who provide stand-alone vision plans say it’s unfair to keep them out of the exchanges because they are paying millions of dollars in additional taxes to support the health overhaul. Attempts to address the issue in Congress have proved futile, as did a recent attempt in the California Legislature.

VSP, the nation’s largest vision care company with 60 million members, had to pay $25 million by Sept. 30 in new federal taxes even though the company is not allowed to sell directly in most states.

“Everyone agrees that stand-alone vision plans should be included,” said Rob Lynch, chief executive of VSP, which is based in the Sacramento suburb of Rancho Cordova. “Everybody points to somebody else as being the responsible party to make that happen.”

Q: Is dental coverage available?

A: Health plans don’t have to include adult dental coverage, only pediatric dental coverage. If your plan doesn’t include adult dental, you can buy stand-alone family dental plans for an additional cost through their state exchange. Some consumers may be drawn to family dental plans if a dentist they prefer is not a provider in their health plan.

Q: I have health insurance through work. Can I check out the exchange to see if that insurance would be better or cheaper?

A: The exchanges are for people who don’t have access to affordable coverage at work. If you lose your job and your health insurance, you can apply for coverage through HealthCare.gov or your state exchange at any time of the year. You’d be eligible for what’s called a “special enrollment period” available to people who experience certain life changes. Coverage through the exchanges is likely to be more affordable than continuing your employer’s plan under COBRA.