The Supreme Court will hear oral arguments Tuesday over the future of the Affordable Care Act — the third time in eight years the ACA has been on the brink of life or death at the high court.The big picture: For now, the smart money says that the court is likely to strike down what remains of the law’s individual mandate, but is unlikely to go along with the argument — advanced by both red states and the Trump administration — that the whole law has to fall along with it.But that conventional wisdom is based on a lot of guesswork. We’ll get a clearer sense of the justices’ thinking on Tuesday, and the answers to these three questions will give us a better sense of what’s about to happen to 20 million people’s health insurance.1. Can the mandate survive?Probably not, but if it can, this case will be easier than almost anyone expects.Red states and the Trump administration argue that because the Supreme Court upheld the mandate as a tax in 2012, it became unconstitutional when Congress zeroed out the tax penalty in 2017.Blue states counter that it still functions as a choice between buying insurance or paying a $0 penalty, and that no one is actually injured by the fact that the coverage requirement is technically still on the books with no penalty to enforce it.2. Whose intent matters?If the court strikes down the mandate, then the question turns to “severability” — how much of the rest of the ACA has to fall along with the mandate.Severability is always a question of congressional intent. The courts try to figure out whether Congress still would have passed other provisions without the one the courts are striking down.Texas and the Justice Department argue that the whole law has to go, and to substantiate that case they point to 2010, when Congress passed the individual mandate, and 2012, when the Obama administration defended it in court.On both of those occasions, it’s absolutely true that Democrats believed the mandate was inseparable from protections for people with pre-existing conditions.The blue states' counterargument: If you want to know whether Congress would have kept the rest of the ACA intact without the individual mandate, that's exactly what Congress did in 2017, when it zeroed out the mandate but left the rest of the law intact.3. Who’s going to save it?Blue states’ argument is based on the kind of textualist, congressionally focused principles that often work with conservative justices. But for the law to survive, at least two Republican appointees have to cross over and vote with the court’s liberals to save it.Most observers expect Chief Justice John Roberts to be one of them. And there are reasons to believe he might find a second.Earlier this year, Justice Neil Gorsuch raised some eyebrows when his approach to the conservative legal principle of textualism led him to a liberal policy outcome. Also this year, Justices Samuel Alito and Brett Kavanaugh joined Roberts in an important severability decision. And Justice Amy Coney Barrett also mentioned the “presumption of severability” at her confirmation hearings.Go deeper: How a conservative Supreme Court could save the ACA