We had two different federal appeals court panels give conflicting rulings on Tuesday regarding the legality of subsidies in the Affordable Care Act. This came about due to some ambiguities in the writing of the law–primarily a proof reading error at one point which suggests that only insurance purchased in state exchanges can allow subsidies. The bulk of the law makes it clear that people purchasing coverage can qualify for subsidies regardless of whether purchased on a federal or state exchange.
It is impossible to predict with certainty, but legal experts are generally predicting that the Supreme Court would follow precedent and go with the overall intent of the law as opposed to allowing the conservative activist judges from the United States Court of Appeals for the District of Columbia to overturn the law.
In the event that the Supreme Court should support this idea we could then have a rather chaotic situation. About 4.5 million people would lose their subsidies, making many people very angry at any Republican politicians who refused to work towards a fix. There would be two potential solutions. One would be for each state to build their own exchange. Presumably they would now have the benefit of the experience of those working on the federal exchange, so this might not be as difficult as it sounds. However, a far simpler solution would be for Congress to pass legislation to clear up the ambiguous wording in the Affordable Care Act which led to this situation.
We could have rather interesting political battles if Republicans would continue to call for repeal and refuse to act to make the fix. This would anger many voters who in effect are receiving a significant tax increase by losing their subsidies, and ultimately might lose their medical care. Would Republicans stick to demanding repeal or be forced to give into demand to allow people to receive the subsidies and continue their insurance coverage? If I was a Republican politician, I think I might hope that the Supreme Court rules in favor of the current subsidies and avoids this political problem.