The result could trigger a complex scenario in which insurers still have to cover virtually anyone regardless of their health status and history, but without a mechanism that requires everyone to participate. And if healthy people don’t have to participate, premiums for everyone else could shoot through the roof as insurers cover more people with serious health problems.

Such a move could force the very same insurers who lobbied Congress for the individual mandate to persuade lawmakers to strip away provisions Obama and others sold as part of a grander bargain to protect patients’ rights — like the requirement to cover everyone with pre-existing conditions.

Private health insurers are nervous about such a scenario. The 18-month-long health reform battle on Capitol Hill left behind scars not easily healed. Now, Democrats and Republicans are so divided over the law that one of the simplest possible “fixes” — the repeal of the widely hated 1099 reporting requirements for small businesses — took months to accomplish.