The debate over President Barack Obama’s health care law has taken another twist. Now conservatives and libertarians are defending it, while the administration tries to toss part of the legislation out.

The reason for this role reversal is that the drafters of the law outsmarted themselves and handed their opponents a weapon. Now they would like to pretend the law doesn’t say what it does.

Obama’s plan makes tax credits available to people who get health insurance from exchanges set up by state governments. If states don’t establish those exchanges, the federal government will do so for them. The federal exchanges, however, don’t come with tax credits: The law authorizes credits only for people who get insurance from state-established exchanges. And that creates some problems the administration didn’t foresee, and now hopes to wish away.