The Affordable Care Act has withstood dozens of repeal attempts in Congress and two strong Supreme Court challenges.

Now the 2010 health law, also known as Obamacare, will have to survive another major test.

On Friday, a federal judge in Texas struck down the ACA as unconstitutional, siding with a group of Republican attorneys general – including Chris Carr of Georgia – who filed a legal challenge to it.

Judge Reed C. O’Connor ruled that the tax bill passed by Congress last December effectively made the whole ACA unconstitutional. That measure eliminated the ACA tax penalty for not having health insurance.

How this latest Obamacare battle will ultimately play out is unclear. If Friday’s ruling is eventually upheld and the ACA disappears, Congress is likely to get involved in creating new health care legislation.  But all that will take time.

So what happens now?

The ruling did not block enforcement of the ACA, so it may not have any immediate effect. But the decision is expected to raise concerns among Americans who get coverage from the health insurance exchange or from states’ expansion of Medicaid programs – both of which were brought about by the ACA.

“The status quo is still in place,’’ said Laura Colbert of the consumer advocacy group Georgians for a Healthy Future. But she also said she was concerned about the confusion and the anxiety that the ruling may create.

“The ACA made it possible for hundreds of thousands of Georgians to get coverage, and any ruling like this is a concern,’’ Colbert said Saturday.

The case will likely end up in the Supreme Court, legal experts say.

Ironically, the Texas decision was handed down on the eve of the final day of enrollment in the exchange. And it comes after a political campaign season in which protections for people with pre-existing health conditions – a guarantee under the ACA – became a major issue.

Seema Verma, the administrator of the federal Centers for Medicare & Medicaid Services, which oversees the exchanges, said in a tweet: “The recent federal court decision is still moving through the courts, and the exchanges are still open for business and we will continue with open enrollment. There is no impact to current coverage or coverage in a 2019 plan.”

Still, the Trump administration said this summer that it would not fully defend the law in court.

The White House said it did not agree that the tax law meant the entire ACA was unconstitutional. But the Justice Department said provisions of the law guaranteeing that people with pre-existing health conditions could purchase coverage at the same price as everyone else were so inextricably linked to the tax penalty that they should be struck down, the New York Times noted.

President Trump, who has consistently sought the law’s repeal, posted on Twitter late Friday night: “As I predicted all along, Obamacare has been struck down as an UNCONSTITUTIONAL disaster! Now Congress must pass a STRONG law that provides GREAT healthcare and protects pre-existing conditions.”

Various national groups representing hospitals, physicians and health insurers denounced the judge’s ruling.

Mandatory health coverage was a central provision of the original ACA, intended to draw healthier people into the insurance pool to help offset the costs of sicker enrollees, the Wall Street Journal reported. But the tax penalty for the uninsured was never very popular, and Republicans in Congress were able to repeal it last year even though they could not get the votes to repeal the entire ACA.

In the new case, the 20 plaintiff states, led by Texas, argued that with the penalty now zeroed out, the individual mandate for coverage had become unconstitutional — and that the rest of the law could not be severed from it.

A coalition of 16 states and the District of Columbia, led by California, intervened and defended the law. They are expected to appeal the ruling.

“Today’s ruling is an assault on 133 million Americans with pre-existing conditions, on the 20 million Americans who rely on the ACA’s consumer protections for health care, on America’s faithful progress toward affordable health care for all Americans,” Xavier Becerra, the California attorney general, said in a statement.

Elizabeth Weeks, a health law expert at the University of Georgia’s School of Law, said Saturday that the decision shouldn’t change coverage for consumers for next year because of expected appeals. “I won’t be surprised if the case winds up in the Supreme Court,’’ she said Saturday.

In the original Supreme Court case on the ACA, Weeks noted, the justices found in 2012 that the law’s provision essentially requiring states to expand Medicaid was unconstitutional (so expansion has been optional since then), but the court upheld the rest of the health law. In Texas, Weeks said, the judge ruled that one part being unconstitutional voided the entire law.

She suggested the judge’s ruling was timed to appear after the election and after the main part of Open Enrollment season for the ACA exchange.

Still, Weeks added, “It certainly puts a big question mark over the law.’’

Carr, the Georgia attorney general, tweeted Friday night: “My colleagues and I argued that the ACA is a constitutionally flawed law, and this federal court ruling validates what we’ve been saying all along.”

If Judge O’Connor’s decision ultimately stands, about 17 million Americans will lose their health insurance, according to the Urban Institute, the Times reported. That includes millions who gained coverage through the law’s expansion of Medicaid, and millions more who receive subsidized private insurance through the law’s online exchanges.

Insurers will also no longer have to cover young adults up to age 26 under their parents’ plans; annual and lifetime limits on coverage will again be permitted; and there will be no cap on out-of-pocket costs. Without those protections, insurers could return to denying coverage to such people or to charging them more. They could also return to charging people more based on their age, gender or profession, the Times reported.

The Kaiser Family Foundation estimates that 52 million adults from 18 to 64, or 27 percent of that population, would be rejected for coverage under the practices that were in effect in most states before the ACA.

“This ruling could send us back to the Wild West of insurance,’’ Colbert said.

Rick Pollack, president and CEO of the American Hospital Association, said late Friday that “the ruling puts health coverage at risk for tens of millions of Americans, including those with chronic and pre-existing conditions, while also making it more difficult for hospitals and health systems to provide access to high-quality care.’’

Dr. Barbara L. McAneny, president of the American Medical Association, said the decision “will destabilize health insurance coverage by rolling back federal policy to 2009. No one wants to go back to the days of 20 percent of the population uninsured and fewer patient protections, but this decision will move us in that direction.”

Matt Eyles, president and CEO of America’s Health Insurance Plans, called the court’s decision “misguided and wrong.”

“This decision denies coverage to more than 100 million Americans, including seniors, veterans, children, people with disabilities, hard-working Americans with low incomes, young adults on their parents’ plans until age 26, and millions of Americans with pre-existing conditions,’’ Eyles said.