There's also the possibility that a Republican administration could follow Obama's example in dealing with the Defense of Marriage Act and simply not defend the law.
Miller calls the government's confidence over the Affordable Care Act's constitutionality "braggadocio" on the part of Justice Department attorneys, something they've shown during the entire process, he says. "This legal team has mostly been overconfident ... they thought they weren't going to have any trouble in the lower courts, and it turns out they misjudged the terrain," Miller says. "Half the time, they've stubbed their toe in the district courts and the court of appeals, but they still think that going to the Supreme Court, they're going to prevail."
Center for American Progress's Millhiser disagrees. "They have every reason to be confident," he says, pointing to past Supreme Court cases he believes have set a precedent for a government victory, like Gonzales v. Raich and United States v. Comstock, both of which upheld Congress's power. "They have so many justices on this court, including the most conservative justices who've said yeah, Congress does indeed have the power to regulate markets, and that includes the national healthcare market."