From the beginning, advocates of universal health care were troubled by the incompleteness of Barack Obama's plan, which unlike those of his Democratic rivals wouldn't cover everyone. But they were willing to cut Mr. Obama slack on the issue, assuming that in the end he would do the right thing.
Now, however, Mr. Obama is claiming that his plan's weakness is actually a strength. What's more, he's doing the same thing in the health care debate he did when claiming that Social Security faces a "crisis" - attacking his rivals by echoing right-wing talking points.
The central question is whether there should be a health insurance "mandate" - a requirement that everyone sign up for health insurance, even if they don't think they need it. The Edwards and Clinton plans have mandates; the Obama plan has one for children, but not for adults.
Why have a mandate? The whole point of a universal health insurance system is that everyone pays in, even if they're currently healthy, and in return everyone has insurance coverage if and when they need it.
And it's not just a matter of principle. As a practical matter, letting people opt out if they don't feel like buying insurance would make insurance substantially more expensive for everyone else.
Here's why: under the Obama plan, as it now stands, healthy people could choose not to buy insurance - then sign up for it if they developed health problems later. Insurance companies couldn't turn them away, because Mr. Obama's plan, like those of his rivals, requires that insurers offer the same policy to everyone.
As a result, people who did the right thing and bought insurance when they were healthy would end up subsidizing those who didn't sign up for insurance until or unless they needed medical care.
In other words, when Mr. Obama declares that "the reason people don't have health insurance isn't because they don't want it, it's because they can't afford it," he's saying something that is mostly true now - but wouldn't be true under his plan.
The fundamental weakness of the Obama plan was apparent from the beginning. Still, as I said, advocates of health care reform were willing to cut Mr. Obama some slack.
But now Mr. Obama, who just two weeks ago was telling audiences that his plan was essentially identical to the Edwards and Clinton plans, is attacking his rivals and claiming that his plan is superior. It isn't - and his attacks amount to cheap shots.
First, Mr. Obama claims that his plan does much more to control costs than his rivals' plans. In fact, all three plans include impressive cost control measures.
Second, Mr. Obama claims that mandates won't work, pointing out that many people don't have car insurance despite state requirements that all drivers be insured. Um, is he saying that states shouldn't require that drivers have insurance? If not, what's his point?
Look, law enforcement is sometimes imperfect. That doesn't mean we shouldn't have laws.
Third, and most troubling, Mr. Obama accuses his rivals of not explaining how they would enforce mandates, and suggests that the mandate would require some kind of nasty, punitive enforcement: "Their essential argument," he says, "is the only way to get everybody covered is if the government forces you to buy health insurance. If you don't buy it, then you'll be penalized in some way."
Well, John Edwards has just called Mr. Obama's bluff, by proposing that individuals be required to show proof of insurance when filing income taxes or receiving health care. If they don't have insurance, they won't be penalized - they'll be automatically enrolled in an insurance plan.
That's actually a terrific idea - not only would it prevent people from gaming the system, it would have the side benefit of enrolling people who qualify for S-chip and other government programs, but don't know it.
Mr. Obama, then, is wrong on policy. Worse yet, the words he uses to defend his position make him sound like Rudy Giuliani inveighing against "socialized medicine": he doesn't want the government to "force" people to have insurance, to "penalize" people who don't participate.
I recently castigated Mr. Obama for adopting right-wing talking points about a Social Security "crisis." Now he's echoing right-wing talking points on health care.
What seems to have happened is that Mr. Obama's caution, his reluctance to stake out a clearly partisan position, led him to propose a relatively weak, incomplete health care plan. Although he declared, in his speech announcing the plan, that "my plan begins by covering every American," it didn't - and he shied away from doing what was necessary to make his claim true.
Now, in the effort to defend his plan's weakness, he's attacking his Democratic opponents from the right - and in so doing giving aid and comfort to the enemies of reform.
Paul Krugman is Professor of Economics at Princeton University and a regular New York Times columnist. His most recent book is The Conscience of a Liberal.
© 2007 The New York Times