"The insurance companies, by the way, were counting on this [surge from young adults], we've had specific discussions with them," he said.
"It's counterproductive," Counihan said of the White House's decision to end scheduled ads, outreach and reminder emails to encourage people to beat Tuesday's deadline and sign up for coverage on HealthCare.gov, which sells plans in 39 states.
"To be frank, I think it's fairly transparent," Counihan said when asked why the White House pulled the plug on that outreach.
"I think the intention is to suppress enrollment," he said. "This has a material impact on enrollment."
"It feels to me that what they're doing is reacting to the fact that there is growth in enrollment," Counihan said of the Trump administration.
A spokeswoman for the the industry group America's Health Insurance Plans, in response to the ads being killed, said, "At a time when the individual market faces challenges,we need as many people as possible to participate — so that costs go down for for everyone."
"Balancing out the risk pool is an important action that can betaken now to help stabilize the market, improve affordability, and send strong signals as health plans develop their products for 2018," said the AHIP spokeswoman, Kristine Grow.
President Donald Trump is a staunch Obamacare foe, calling the program a "disaster" in a speech in Philadelphia on Thursday. Trump has called for the Affordable Care Act to be quickly repealed by Congress and replaced with a better plan, but so far has not unveiled the details of that plan.
HealthCare.gov and the other Obamacare exchanges run by individual states and the District of Columbia so far this enrollment season had signed up more than 11.6 million customers, putting them on track to beat last year's enrollment tally somewhat, before Thursday's move by the White House. HealthCare.gov alone accounted for about 8.8 million of the tally to date.
Counihan and others have pointed to the healthy pace of sign-ups as proof that Obamacare is not failing, much less in a "death spiral" that results when not enough healthy customers are in insurers' risk pool, leading to higher premium rates.
"The problem here is this is literally yanking, like a minute before midnight," messages that could bolster sign-ups and improve that risk pool, Counihan said. But he added that Obamacare advocates, including navigators who help people enroll in individual health plans, are "doubling down on outreach" because of the White House's decision.