As the Supreme Court considers the constitutionality of the federal health care law, one option that had seemed unthinkable to its designers and supporters now seems at least possible: that the court could strike down the entire law.

Although it would be folly to predict what the court will conclude, policy experts, insurers, doctors and legislators are now seriously contemplating the repercussions of a complete change in course two years after the nation began to put the law into place.

Their concerns were heightened after three days of court arguments in which some justices expressed skepticism about whether the full law could stand without the individual mandate requiring almost everyone to have insurance.

“Many of us did not get the bill we wanted, but I think having to start over is worse than having to fix this,” said Robert Laszewski, a health care industry consultant and former insurance executive who opposed the bill.