Health and Human Services Secretary Alex Azar, boasting about results on a press call with reporters, said President Donald Trump “the president who was supposedly trying to sabotage this law has been better at running [Obamacare] than the guy who wrote the law.”

Obamacare supporters have said the improving marketplaces are largely a sign of the law's maturing, and that the Trump administration has taken steps to undermine the law. The administration "deserves zero credit" for the law's success, said Protect Our Care, a Democratic-aligned group formed to defend Obamacare.

Premiums rose sharply in the first years of Obamacare as insurers adjusted to new rules. Insurers also hiked their rates in Trump's first year amid congressional Republicans’ failed effort to repeal the law and numerous steps taken by the administration seen as undermining the marketplaces.

The marketplaces have calmed since then. Insurers have learned more about the health needs of their customers, and large subsidies have protected most enrollees from huge rate hikes. HHS under the Trump and Obama administrations has also approved reinsurance programs that help insurers cover the cost of their most expensive customers.

The average premium for the benchmark plan, which is used to calculate subsidies, will drop from $406 to $388 in states relying on the federal enrollment platform, HHS said. Delaware led all states with a 20 percent decrease in its average premium, in part because the state implemented a reinsurance program.

About two-thirds of enrollees receiving subsidies, who make up about 87 percent of the market, will pay less than $75 per month in premiums if they keep the same level of coverage, and about one-third will pay under $10 per month.

Of those earning too much to receive federal help, more than a third will pay over $500 per month in premiums. About another third will pay between $300 and $500.

“These premiums are still unaffordable by many,” Azar said, contending that the law remains fundamentally flawed and must be replaced. “This is not a workable way for Americans to finance the care they need … but we are headed in the right direction.”

High out-of-pocket costs continue to be a challenge. The median deductible for mid-level "silver" plans in the insurance marketplaces is more than $4,600, up 3 percent from this year.

It's possible a federal appeals court could issue a decision on the validity of the Affordable Care Act by the time enrollment opens Nov. 1. The 5th U.S. Circuit Court of Appeals is reviewing a decision from a federal judge who found the entire law was unconstitutional.

The Trump administration has said it will continue to enforce the health care law while the legal challenge winds through the courts. The final word is likely to come from the Supreme Court next year.

