Encourage insurance companies in wobbly markets?

There are smaller decisions ahead, too, about how to administer programs, whether to enforce the law’s individual mandate, and whether to recruit insurers to participate in markets where competition is thin.

So far, Mr. Trump’s secretary for health and human services, Tom Price, has taken every opportunity to gloat about the health law’s setbacks, even as he is administering its programs.

Mr. Price, perhaps more than Mr. Trump, has long been committed to the Affordable Care Act’s demise. But now he will have to manage the law’s many programs. Obama administration officials called insurers, cajoling and reassuring them. If Mr. Trump wants the markets to be vigorous, he could use his self-described deal-making skills to woo insurance companies into the stabilizing markets.

Make the system more conservative?

If Mr. Trump and Mr. Price can make peace with the health law, there are opportunities to steer it in a more conservative direction. The law gives broad authority to the executive branch to shape health care policy. So far, the health law has been driven by Obama administration priorities, but that could change.

A few early regulatory changes have begun that process. The Trump administration plans to make it harder for people to sign up for plans midyear. It has given insurers more wiggle room to raise their deductibles. It may be able to make alterations that loosen up benefit requirements — though it won’t be able to completely eliminate them, as Republicans sought to do at the last minute in the failed bill.

Offer states maximum flexibility?

The administration will also have enormous power to allow states to reshape their Medicaid programs — and even their local insurance markets — through waivers to existing law. Seema Verma, the just-confirmed administrator of the Centers for Medicare and Medicaid Services, was a consultant who helped states write pathbreaking conservative proposals for their Medicaid programs. She is ideally positioned to approve many more such waivers from Republican-led states, allowing them to impose premiums, cost-sharing and even work requirements for Medicaid beneficiaries.

A new Obamacare waiver program has just gone into effect: It would allow states to overhaul their entire health insurance markets if they can show that their revised plans would cover as many people. That process could allow Ms. Verma and Mr. Price to approve state plans that hew more closely to the Republican vision for health care.