Much of the news lately about the Affordable Care Act, also called Obamacare, has been about the troubled rollout of the web marketplace enrollment and the cancellation notices going out to a segment of the 5% of Americans who get coverage from the individual health insurance market. (Read this for an accurate explanation of what is going on with the cancellations. And this about President Obama's announcement of a policy change that may allow some people to keep their cancelled policies for at least another year.)  But there is another Obamacare story that has gotten much less attention: enrollment in Medicaid, which is being expanded in many states, is going like gangbusters.

Nine out of 10 new Obamacare enrollees have signed up for Medicaid, the Washington Post reports, compared to only "a trickle of sign-ups for private insurance." Oregon, for instance, cut its uninsured "without signing up a single person for private health insurance."

This is a potentially watershed development, because Medicaid is Obamacare's only true public option: a program jointly administered and funded by federal and state governments. (Although many liberals had sought to have another public option added to compete directly with the private plans offered in the state marketplaces, that version of a public option never made it into the final law). But Medicaid, which even before the ACA was the largest insurance program in the United States with 62 million enrollees, is central to Obamacare's goal of providing health insurance to nearly all Americans.

Under the ACA as originally written by Congress, Medicaid eligibility would have been expanded to all persons with incomes up to 138% of the federal poverty level (about $27,000 for a family of four), paid for almost entirely by the federal government. States that didn't go along would have been penalized by losing all of their current Medicaid funding. But the Supreme Court, in its decision last year to uphold the rest of the ACA, said that it was unconstitutional for the government to impose penalties on states that don't expand Medicaid, making it a purely voluntary public option--states can to take or leave it.

Perhaps it is not so surprising if Medicaid enrollment takes off in the 21 states, including New Jersey, that have agreed to expand eligibility. But Medicaid enrollment is likely to go up even in states like Pennsylvania that have not yet agreed to the expansion, because the ACA makes the Medicaid enrollment process easier in every single state. The non-expanding states will get more Medicaid enrollees but without any additional federal expansion money. Pennsylvania Governor Tom Corbett has proposed using the federal expansion money to enroll people in private health insurance plans offered through the Obamacare marketplace, although this would require approval by the legislature and then by the federal government, and some experts say it is doubtful that his "private option" will save the state money as he claims.

The lopsided enrollment trends in Medicaid compared to private insurance may change when the problems with the enrollment site are fixed and people can more readily shop around and sign up for a marketplace private plan. It is also possible, though, that we are seeing what liberals have long hoped for and conservatives have long feared: that if people are offered a chance to easily enroll in a public plan (Medicaid) that generally offers better benefits and is cheaper than private insurance, they will jump at it, compared to the complexity of navigating a maze of private insurance companies that cost more and offer fewer benefits. (The higher-than-expected Medicaid enrollment trends are happening in states that are running their own marketplaces and are not dependent on the federal government's balky enrollment web portal).

If this is so, conservatives might rue the day that they rooted for Obamacare's website to fail and for its marketplace private insurance enrollment to tank. Rather than disproving government-run healthcare, a failure of the ACA's private insurance marketplace enrollment process might make the case for further expanding Obamacare's other, much simpler public option, which is to make it as easy as possible for people to sign up for public health insurance in the form of Medicaid. In other words, single payer health care.

From Obamacare to Medicare to managed care, read more of The Field Clinic here »