Ezra Klein explains.

Its failing, somewhat ironically, is a lack of audacity. It accepts the sectioning off of the market into the employed, the unemployed, the old, the young, and the poor. It does not consolidate the system into a coherent whole, preferring instead to preserve the patchwork quilt of programs and insurers that make health care so difficult to navigate. It does not sever the link between employment and health insurance, nor take a firm step towards single-payer, despite Obama’s professed preference for such a system.

All the ingredients are in place for this to be a great plan — a public insurance component, a commitment to universality, an understanding that coherence is better than fractiousness, a willingness to regulate the insurance industry — but, in each case, at the last second, the policy is hedged before the fulfillment of its purpose. In this, Obama’s plan is not dissimilar from Obama himself — filled with obvious talent and undeniable appeal, sold with stunning rhetoric and grand hopes, but never quite delivering on the promises and potential. And so he remains the candidate of almosts. But as he told Morgan Miller back in March, there is time yet. And he is so very close.