The latest Obamacare challenge: What you need to know

In 2012, the Affordable Care Act barely survived a constitutional challenge when Chief Justice John Roberts stunned conservatives and voted along with the court’s four liberal justices to uphold the law.

On March 4, the justices will gather again to hear a challenge to the law, based on the validity of subsidies in the form of tax breaks, that could affect millions of Americans.

What’s all the fuss about?

The health care law provides for the establishment of “exchanges” through which individuals can purchase competitively priced health insurance. It also authorizes federal tax credits to low- and middle-income Americans to help offset the cost of the policies.

Currently 16 states plus the District of Columbia have set up their own exchanges; the remaining 34 states rely on exchanges run by the federal government. r

But in order to bring the challenge, the plaintiffs have to show that they have the “standing” or legal right to be in court. This means that they have to have been harmed by the government action.

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Although the lower courts dismissed the government’s argument that the plaintiffs didn’t have standing, the media and others have uncovered information that could raise new questions. It turns out, for example, that two of the plaintiffs are veterans and could be eligible for health care through the Department of Veterans Affairs, though they signed a declaration swearing that they weren’t eligible for government insurance. If they were, they wouldn’t have to buy insurance through the exchange.

As things stand now, however, the government has not pressed the issue before the Supreme Court. But the justices themselves might be interested in the issue, which could potentially derail the case.