WASHINGTON — The Republican tax bill that now appears headed to final congressional approval and the president’s desk includes repeal of the universal mandate, the foundation upon which Access Health CT and all Obamacare exchanges were built.

Removing the requirement that all must have health insurance or pay a tax penalty may be good news for the young and healthy or those who don’t want to pay for coverage, for whatever reason.

But for Access Health CT, the loss of the mandate is a torpedo in the side of the risk-pool superstructure that keeps it afloat, officials say.

“It will disincentivize people who are healthy, which will drive up costs for people who do sign up,” said Vicki Veltri, chief health policy adviser to Lt. Gov. Nancy Wyman. “It also disincentivizes people who don’t get insurance until they are sick.”

The insurance risk pool depends on a balance of healthy and sick individuals paying into a common fund, Veltri said, adding: “If you wait until you need it, it increases your cost and everyone else’s.”

The mandate formed the basis of Obamacare from the day it was signed into law in 2010. Republicans have been looking to overturn it ever since. The Supreme Court in 2012 upheld the mandate as a legitimate form of government taxation.

President Donald Trump campaigned on repealing Obamacare altogether. And Senate Majority Leader Mitch McConnell said last summer that Republicans “agree on the need to free Americans from Obamacare’s mandates (so that) Americans are no longer forced to buy insurance they don’t need or can’t afford.”

Although it passed the House, the effort faltered in the Senate. But the controversial tax bill, which on Friday appeared to get the votes it needed for final passage, became a GOP vehicle for getting at the mandate — Obamacare’s key ingredient.

Connecticut was one of 11 states to set up its own health care exchange in which individuals and families not covered at work could shop for a plan that worked for them. It’s been held up as a successful model, even as Republicans declared the Affordable Care Act a failure and Trump called it “a nightmare.”

As of Friday, Access Health CT had 98,376 enrollees with a week to go before enrollment ends.

About 75 percent of those receive some form of subsidy to help pay premium costs. In addition, 217,066 in Connecticut are getting health insurance through expanded Medicaid, which covers individuals just above the income level cutoff for low-income families receiving regular Medicaid.

Those whose incomes exceed the subsidy limit find themselves facing double-digit percentage increases in premiums from the two companies on Access Health CT, Anthem and ConnectiCare.

Without the mandate, the rise in premiums is likely to get worse, Veltri said. She cited a CBO study that concluded repeal of the mandate would cause premiums to rise an average of 10 percent a year and leave 13 million fewer people nationwide without insurance.

But despite the loss of the mandate, health care experts said they expected Affordable Care Act coverage to survive in Connecticut and elsewhere.

“My best guess if the individual mandate is repealed: The number of uninsured rises, likely by millions,” said Larry Levitt, senior vice president at the Kaiser Family Foundation, which tracks health care issues. “Some insurers drop out, leaving some (mostly rural areas) bare. Premiums rise, but there’s no death spiral because premium subsidies rise too. The ACA is hobbled, but not dead.”