WASHINGTON — As supporters of the Affordable Care Act brace for new headaches next year, many have concluded they cannot count on the Obama administration, whose efforts to explain and promote the law are increasingly viewed as poorly planned, unreliable and largely ineffective.

Consumer advocates, doctors groups and many health industry leaders remain committed to helping the law succeed. Most believe in its goals of expanding health coverage and restructuring the medical system to improve quality and control costs. Few see any viable alternatives.

But even as President Obama launched another attempt last week to rally Americans behind the law, many of his allies believe his administration is no better prepared for the inevitable challenges of moving millions of people into new health plans than it was for the rollout of the federal HealthCare.gov website.

"The refrain we most often hear is: 'Where is the administration?'" said M. Ryan Barker, vice president of the Missouri Foundation for Health, which has been working for nearly four years to help smooth implementation of the law in the state. "It is very frustrating."

Like many of the law's backers, foundation leaders have decided they and their local partners must take responsibility for educating consumers about their new coverage and responding to questions and complaints because the Obama administration has shown little ability to do it.

Many physician groups, hospitals and insurers have come to the same conclusion.

"I have never seen medical providers more dismissive of a White House," said one longtime healthcare lobbyist, who asked not to be identified in speaking so frankly about the president's leadership.

A health industry chief executive who supports the law bemoaned the Obama administration's lack of preparation for even foreseeable complications, such as the recent cancellations of millions of health insurance plans that don't meet the law's new standards. "There just doesn't seem to be much strategic thinking," he said.

White House officials acknowledge the disastrous debut of HealthCare.gov has made it difficult to highlight the law's benefits and respond to criticisms. But they say they are now prepared for a sustained campaign through next year, building on their work with advocates nationwide to enroll people in health coverage.

David Simas, senior advisor to the president on healthcare, said this new sales effort will not only showcase people who are benefiting from the law, but also compare the new protections with the shortcomings of the prior system, which left millions of Americans without health coverage.

Starting in 2014, health plans will be prohibited from turning away sick customers and will have to offer a basic set of benefits, including coverage of prescription drugs, hospitalizations and preventive care.

"Now, we can begin to tell a story," Simas said. "We just have to execute. Period.... That's what we're going to do. We're going to execute on that day after day after day after day."

The White House last week publicized some of its efforts to protect the law from more political trouble. The administration is distributing talking points to Democrats and other allies, as well as hosting daily calls with advocates and key lawmakers to coordinate messages and responses to critics, an official said. And a former White House liaison to Capitol Hill who worked to pass the law, Phil Schiliro, will return temporarily to coordinate strategy with congressional Democrats.

Several administration allies in Washington said they are hopeful this campaign may be more successful.

"I don't want to be Pollyannaish about this, having gone through great difficulties in the past, but I feel better than I've felt in months," said Neera Tanden, president of the Center for American Progress and a former administration official.

Many advocates and industry leaders who support the Affordable Care Act also believe the law's benefits will become clearer to Americans as more experience the security of health coverage, especially if they are ill.

"A lot of people are going to be pleasantly surprised by how good the coverage is," said Daniel Zingale, senior vice president of the nonprofit California Endowment, which has committed more than $200 million to help implement the law in the state.

Indeed, despite the problems with the launch of HealthCare.gov, the online insurance marketplace for consumers in 36 states, there has been strong interest, with hundreds of thousands of people a day viewing the federal site and similar state sites.

But experts acknowledge public appreciation will take time. "We are in the beginning of a very long-term transition in the nation's healthcare system," said Dan Mendelson, chief executive of Avalere Health, a Washington-based consulting firm.

In the interim, many supporters worry that more bumps in the law's implementation could further undermine public confidence, especially without a sustained, strategic plan from the Obama administration.