So there remains a strong possibility that, in the face of enormous political pressure in the administration’s early days, Trump and Congress could pursue a sudden, complete repeal, or something resembling one. In that scenario, the most pressing concern would be the immediate defunding of state health care exchanges, which would potentially remove 20 million people from insurance rolls. Abruptly ending the individual insurance mandate, too — something Trump has said he will do — could cause millions of people to end their insurance.

For insurance companies that participated heavily in Obamacare, a full repeal early in Trump’s tenure would be a nightmare scenario, said the industry source, causing a sudden and dramatic loss of revenue.

“I’m not sure that they’re ready for the full repeal,” said a senior health care industry official of insurers like Blue Cross Blue Shield and Anthem, who have invested heavily in the ACA. “They totally changed their business model” for the ACA, the official said.

An ACA repeal would come with some substantial tax breaks for insurers and pharmaceutical companies, which have been paying into the ACA. And drug companies will likely be able to continue their practice of raising prices on drugs they own, something that was not likely to continue under a Clinton administration — a fact that sent pharmaceutical stocks rising sharply Wednesday in the wake of Trump’s election.