(Charles Dharapak)

But one of the Affordable Care Act’s biggest supporters refuses to jump on the bandwagon.

Blue Shield of California has, among health plans, been one of Obamacare’s biggest cheerleaders. But executives there worry that any promise to continue with a few Affordable Care Act benefits, regardless of what the Supreme Court does, could undercut the case for leaving the law standing.

“We hope the Affordable Care Act will be upheld,” said Steve Shivinsky, Blue Shield of California’s vice president for corporate communications. “We won’t say anything before the decision that would make it easier for the court to rule against the law.”

Blue Shield’s fears, however, are already being realized. Republicans have used the health plans’ new commitments as evidence that Obamacare is unnecessary. Michael Steel, a spokesman for House Speaker John Boehner (R-Ohio), told Politico that the announcements serve as “a reminder that sensible health care reform does not require the massive government takeover in the Washington Democrats’ law.”

Why use government mandates, after all, to accomplish something that private business will do voluntarily?

It’s worth looking here at what, exactly, health insurance plans have volunteered to do. They have committed to implementing a few small parts of the law that are already in effect, such as allowing young adults to stay on their parents’ plans up to age 26 and not charging co-pays for preventive services.

There’s a much longer list of what they have not volunteered to do, a topic TNR’s Jonathan Cohn and WSJ’s Anna Wilde Mathews have both written on. No one has volunteered to end denial of coverage for pre-existing conditions, as Obamacare would in 2014. No plan has promised to subsidize health insurance for low- and middle-income Americans, another provision set to start two years from now.

The health reform law requires, right now, that insurers spend 80 percent of every premium dollar on medical care (as opposed to profits or administration). That’s another one that isn’t on the insurers’ list. If the Supreme Court overturns Obamacare, all of these bigger parts of the act will still land on the cutting-room floor.