In a step some analysts say reflects political posturing, nearly all commercial insurers in Massachusetts now have pledged to continue two popular provisions of the Affordable Care Act even if the Supreme Court throws out the federal health law.

The Massachusetts Association of Health Plans said Monday that all of its members would continue to cover preventive services outlined in the law without requiring copayments, following an announcement Friday by the largest commercial insurers in the state. The insurers also would allow young adults up to age 26 to remain on their parents’ health plans, though state law requires such coverage within that age group only up to two years after they lose tax status as a dependent.

The promise extends only to those people who buy insurance as individuals or who are covered through a small business insurance market regulated by the state. If the law is overturned, large businesses that are self-insured, which cover most people in the United States with employer-sponsored plans, would decide for themselves whether to continue the benefits required under the Affordable Care Act.

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The state health plans association surveyed members to find agreement on which provisions of the law should continue. Members include Aetna, Boston Medical Center HealthNet Plan, CeltiCare, Fallon Community Health Plan, Harvard Pilgrim Health Care, Neighborhood Health Plan, Tufts Health Plan, and United Healthcare.

President Lora Pellegrini said a decision by the court to throw out all or part of the law would create confusion. The announcement Monday is “an effort to really allay fears of consumers and employers, when the decision comes down, about what their coverage would look like and to try to provide some clarity,” she said.

Blue Cross Blue Shield of Massachusetts, not a member of the association, also has said it would continue the two provisions for those in the individual and small group market. That leaves Cigna.

“Cigna believes in respecting the court’s process,” spokesman Jon Sandberg said in an e-mail. The insurer is “prepared to proceed as appropriate on behalf of our customers when the court deliberations reach their conclusion.”

Nancy Turnbull, senior lecturer and associate dean at Harvard School of Public Health, said the promise not to roll back coverage is a good choice but not necessarily a hard one for insurers to make. Premiums now reflect the cost of covering preventive services with no cost to consumers and she wouldn’t expect premiums to drop if the law is revoked, she said.

Some insurers may be preparing for a backlash if the law is overturned and people find their benefits dropped or reduced. The latest announcement is “good politics on their part,” Turnbull said.