A year after their disastrous launch, health insurance marketplaces created through the Affordable Care Act will reopen to consumers Saturday in a high-stakes new test for the health law and its ambitious program for expanding coverage to millions of Americans.
The marketplaces are far more stable than last fall, when the meltdown of HealthCare.gov and several state-run websites threatened a key pillar of the law.
More than 7 million people have gained insurance through the markets. Additional insurers are offering plans in 2015, providing more choices.
And modestly priced premiums should be available to many customers, though consumers may have to shop around to ensure they get savings.
The second enrollment period — which will run through Feb. 15 — faces other, substantial challenges as well.
Re-enrolling millions of people who have coverage and signing up millions more remains a gargantuan task. The Obama administration lowered next year's enrollment target this week from 13 million to fewer than 10 million.
At the same time, the law continues to face strong political opposition from Republicans, who have pledged to use their majorities in Congress next year to resume efforts to dismantle it.
Also shadowing the enrollment period is a new legal threat, which could take away the government subsidies that millions rely on to pay insurance premiums. A lawsuit challenging these subsidies in most states is scheduled to be heard by the Supreme Court this spring.
"The marketplaces have become the litmus test for the law," said Dr. David Blumenthal, a former administration official who heads the Commonwealth Fund, a New York-based health policy foundation. "It is very important that they be successful."
The marketplaces — a centerpiece of the program for guaranteeing health coverage — allow Americans who don't get health benefits at work to shop among plans that must meet basic standards and cannot turn away people with preexisting medical conditions.
Consumers making less than four times the federal poverty level — or about $94,000 for a family of four — qualify for subsidies.
The marketplaces were generally successful in their first year, as enrollment surpassed expectations.
More than 7 in 10 Americans who bought coverage ranked their insurance as "excellent" or "good," according to a new Gallup poll.
And combined with Medicaid expansions in some states, the marketplaces helped cover about 10 million previously uninsured Americans, surveys indicate.
California is among 13 states, including Connecticut and Maryland, that along with the District of Columbia will operate their own markets rather than rely on the federal HealthCare.gov site. After signing up 1.2 million customers, California also became a national model.
Even with the successes, however, many supporters say the second enrollment period may be more difficult.
Persistent problems with government data systems threaten to complicate the process of renewing plans for millions of people who got coverage this year.
Unless consumers go back to the marketplaces to select a plan, their existing plan will be automatically renewed.
That could mean hefty premium hikes, even though many consumers could probably find a cheaper alternative. "We want people to do careful shopping to make sure they get the best possible deal," said Ron Pollack, executive director of Families USA, a leading consumer group.
Pollack and other advocates also concede that reaching new enrollees this season won't be easy as the enrollment period is only three months long, half the duration of last year.
"We are realizing we are going to have our hands full," said Jodi Ray, project director for Florida Covering Kids & Families.
Enrollment activists will contend with new threats from congressional Republicans, as well.
This week, Sen. Mitch McConnell (R-Ky.), the incoming majority leader, pledged new votes to roll back the law both in whole and in part. "Virtually all of us would like to see it pulled out root and branch," he said at the Capitol on Thursday.
A full repeal remains unlikely, as Republicans won't have a veto-proof majority. Even making small changes to the law could prove difficult.
But the threats, combined with the looming Supreme Court case, may dissuade some people from signing up, supporters of the law fear. The case before the Supreme Court, to be decided in June, could ban subsidies for consumers in 37 states that rely on federal marketplaces.
Health and Human Services Secretary Sylvia Mathews Burwell has stressed that consumers shouldn't worry that they will lose government subsidies.
"We are confident that we are going to have a successful open enrollment," Burwell said at the Center for American Progress in Washington this week.
Federal and state officials have made a host of technology upgrades to prevent major system crashes, and they have simplified the application process.
A new shopping tool at HealthCare.gov allows consumers to see what plans will be available without going through the laborious process of setting up an account.
Most Americans will find more health plans on the marketplaces, especially in states such as New Hampshire or Mississippi that had few options in 2014.
They should also have more help. Marketplaces have beefed up call centers and helped train thousands of agents, brokers and other advisors.
At the same time, a vast enrollment effort is gearing up involving thousands of hospitals, pharmacies, churches and community groups. Insurance companies, which played a pivotal role this year in signing up people and working around persistent problems with government enrollment systems, are poised for another big campaign.
And in several states, consumers will have new resources, including Massachusetts, Oregon and Maryland, where the marketplaces barely functioned last year.
Potentially most importantly, premiums remained relatively stable nationally, though consumers will see widely different rates.
For example, a 40-year-old nonsmoker making $60,000 a year in Anchorage will see the monthly premium for the cheapest plan jump from $310 to $396, according to an analysis by the nonprofit Kaiser Family Foundation.
By contrast, the same-aged shopper in Denver will see the monthly premium for a comparable plan drop from $186 to $167.
It is a very different story for a 40-year-old nonsmoker making just $30,000 a year, an income that makes government subsidies available.
The same health plan in Anchorage would cost this lower-income shopper $116 after including the subsidy, 17% below the cost of a comparable plan in 2014.
Such a person in Denver would pay $164 a month with a subsidy, 13% more than in 2014.
"How you will fare will depend on where you live and whether you will be eligible for subsidies," said Cynthia Cox, a senior policy analyst at the Kaiser Family Foundation.