The key to the plaintiff's argument in the
King v. Burwell challenge to Obamacare before the U.S. Supreme Court is that Congress really meant to limit federal subsidies just to the states that set up their own health insurance exchanges because they wanted to force all of the states to set up exchanges and were putting in place a way to punish states that didn't—withholding subsidies from the residents of those states. Their case, they argue, will give Congress and the states the opportunity to "fix" how the law has been implemented to reflect the will of Congress.
Never mind that the actual members of Congress who wrote the bill have clearly and repeatedly stated their intent was to make sure that no states—or people—would be left out, opponents of the law persist in their argument. To the end of debunking it, and providing more information for the justices to consider, a number of journalists and analysts have been combing the real-time record of the legislation making, all finding that there was no indication ever in the process that Congress was considering punishing states. To add to that pile, Theda Skocpol of Harvard University looked at every Congressional Budget Office report from the legislative process. She found 68 reports, and not a single one of them discussed limiting subsidies to just the states with their own exchanges.
That matters because the CBO games out how various policy options members of Congress submit to them will cost. In all of the 68 reports they generated, no member ever asked them to look at what the impact of not providing subsidies in all states would be. That's pretty strong evidence that Congress intended to write the law as it was implemented, with a federal exchange to back up states that didn't want to take on the task and subsidies available to everyone. In Skocpol's words,
"The larger truth is that no one assumed every state would do this. […] It wasn't an issue of politics then, it was one of policy: these were smaller states and there was a thought some of them wouldn't be able to manage the process. It was taken for granted by all parties that some states would need a backup."
It was even taken for granted by
Republican Rep. Paul Ryan at the time, when he complained about the American taxpayer picking up the tab for a "new open-ended entitlement that basically says to just about everybody in this country, people making less than $100,000 […] [t]axpayers got you covered. Government's gonna subsidize the rest." Of course, that didn't stop the 2014 version of Paul Ryan from filing a brief in the case supporting the plaintiffs and now saying that what he said then is totally irrelevant to now.