The legal challenges say that a provision in the law that references the payment of credits to people who enroll through “an Exchange” that is “established by a State” means that credits are not available in the 36 states that have decided to have the federal government manage their exchanges for them.

We are economists, not lawyers. But we note that the statute, while vague at points, confirms, when read in its entirety, that tax credits are to be available on all the exchanges, nationwide. The law specifically instructed the secretary of health and human services to create and manage the exchanges for states that chose that option. And when the law was passed, everyone involved in the law’s passage understood that this directive vested federal exchanges with the same mission and authority as state-mandated exchanges.

The expansion of coverage rests on interlocking elements. The law bars insurers from denying coverage to people with pre-existing medical conditions, dropping coverage when people develop costly illnesses, and charging discriminatory premiums. By themselves, these provisions would encourage people to delay buying insurance until they became ill, causing premiums to skyrocket. So to keep premiums affordable, the law requires nearly everyone to buy insurance, and offers low- and moderate-income people financial help — in the form of refundable tax credits. If both the sick and the healthy buy insurance, premiums can be kept within reason.

Limiting tax credits to the 14 states that manage their own exchanges (along with the District of Columbia) would destroy this careful architecture. Over five million people receive coverage through federal exchanges — two-thirds of all those covered through exchanges and 40 percent of those newly insured by the act. The best estimates suggest that out-of-pocket costs to typical enrollees of the least-expensive plans available in federally facilitated exchanges would soar to 23 percent of household income, from 3 percent — and to 28 percent of income, from 6 percent, for those in the second least-expensive plans. Households would lose about $36 billion in tax credits that help make insurance affordable. Some 6.5 million fewer people would be insured. The federal exchanges could collapse, because they would be left with sick patients, saddled with costly premiums.

The record is unambiguous: Congress, in 2010, understood and endorsed the links connecting the sale of insurance, the requirement to carry insurance and the financial aid to make it affordable. Opponents who lost in the democratic process are now seeking to vitiate the law through a perverse reading of it.