WASHINGTON — The Supreme Court is expected to announce on Thursday morning its decision on the health care overhaul that President Obama signed into law in 2010 — an act of Congress thousands of pages long, containing hundreds of changes costing hundreds of billions of dollars and affecting nearly every American from cradle to grave.


But the nine justices are expected to answer only a few principal questions, stemming from a handful of conflicting lower court decisions. Although the arguments are complex, the questions are fairly straightforward.


First, and perhaps above all, did Congress overstep its powers when it passed the “individual mandate” requiring virtually all Americans to obtain health insurance or pay a penalty? If a majority finds that it did, the most prominent feature of the law will be overturned.


Second, if the justices strike down the mandate, what other parts of the law are so closely tied to its centerpiece that they must also fall? Both the Obama administration and the law’s opponents have argued that two other provisions — requiring companies to sell policies to anyone who applies and prohibiting insurers from charging extra to sick people — should fall, to keep the insurance market functioning.


But not all experts agree with that argument, and the justices could decide to strike down only the mandate — or to strike down the entire statute.


Third, does the court even have the standing to consider the mandate now? The justices could deem the penalty tied to the mandate to be a tax and announce that it is too early to decide the mandate’s fate, because the first penalties will not be due until 2015. An obscure statute, the Anti-Injunction Act, holds that challenges to taxes are barred until they are due.


Finally, did a major part of the bill separate from the mandate — an expansion of Medicaid, covering millions of additional lower-income people — amount to federal coercion? As part of the change, Congress increased aid to states but also said that their existing Medicaid financing would be at risk if the states did not accept their new obligations.


On the first day of oral arguments, in March, the justices appeared to give short shrift to the notion that the law was not ready for appeal. On the second day, their sharp questioning of the administration’s chief advocate, especially by Justice Anthony M. Kennedy, the court’s swing vote, suggested skepticism and perhaps discomfort with the mandate — even hostility from the conservative wing — but the four liberals seemed solid in their support. On the third day, the justices also seemed divided on what should happen to the rest of the law, including Medicaid.


After the arguments, any consensus about what the court would do seemed to have been shattered. The speculation will continue right up to 10 a.m. on Thursday, when the justices assemble for the final day of the term.


The court has two other rulings still on its docket, including one on a case dealing with the legality of lying about military medals. Most observers expect those rulings to be announced first, which would extend the wait for the health care ruling just a bit longer.


Based on the massive record, specialists in health care and the law have come to focus mainly on a handful of the most plausible outcomes.


A majority on the court might reject the fundamental overhaul of insurance that lies at the heart of the law, finding its mandate that everybody obtain insurance to be unconstitutional, and perhaps dismissing as well the closely related requirements that insurers cover everybody who applies and not charge sick people more. Much or even all of the rest of the law might be left to stand — if it survives politically. Depending on the particulars, this would be a defeat, but not necessarily a rout of the Obama administration and its supporters. It would be a notable exercise of judicial power.


The court might go even further, declaring that without the insurance provisions the rest of the statute would never have passed Congress in the first place and that the whole bill should be rejected; the most definitive possible outcome, its very bravura makes it less likely. Or the court might essentially punt, accepting the argument, as one lower court did, that it was too soon to decide this case; that, too, seems hardly likely, given how these cases sped through the courts and how enthusiastically the Supreme Court joined the issues. It would keep the bitter partisan debate over the law going full tilt through the November elections and beyond.