Tomorrow, the Supreme Court will hear oral arguments on the constitutionality of the individual mandate — the legislative machinery at the heart of Obamacare.

Tomorrow’s argument could lead to some of the most momentous pronouncements from the high court on the limits of federal power and the proper nature of the safety net that we’ve seen in American history.

So here are a couple of things to look for during tomorrow’s arguments for clues as to how SCOTUS might rule.

* At some point, Paul Clement, the lawyer arguing the case against the law, will argue that the individual mandate represents unprecedented intrusion into the private decisions of Americans. If it is allowed to stand, he’ll say, there will be no limit on what Congress can force you to do.

This is the argument against Obamacare that has been accorded merit by lower courts. “To the extent that judges have been sympathetic to this case, this is what they’ve been receptive to,” Ian Millhiser, senior constitutional policy analyst at the Center for American Progress, tells me.

Obamacare’s defender will closely monitor the reaction to this argument from justices Roberts, Kennedy, and Scalia. If one or more of them greet it with skepticism and subject it to sharp questioning — for instance, by pointing out that the health care market is unique, because everyone must ultimately partake of health care — that’s good news for Obamacare proponents.

* This leads to the next, and perhaps more significant, clue to watch for. At some point, the lawyers defending the law will be asked by the justices what the federal government cannot force Americans to do if the individual mandate is deemed constitutional. This question — a challenge that the Obama administration state unequivocally what the proper limits on federal power are — could decide the court's ruling.

The law’s defenders will respond that the individual mandate does not inevitably imply a federal government that, under the commerce clause, can usurp the power of the states in regulating or compelling individual behavior. The legal brief filed by the Obama administration defending the law justifies this by pointing out that the commerce clause does not empower the federal government to regulate areas such as family law, general criminal law, or education.

Defenders will point this out again in court tomorrow. Their argument will be that health reform is addressing a problem that’s fundamentally national in nature; that the federal government already plays a large role in regulating health care matters; and that the individual mandate would not imply a federal government that can trample on areas where states have historically held sway.

The question is how the key justices react to this argument. If they seem to find it convincing, that means they are accepting the idea that a constitutional individual mandate does not set precedent for the government having unlimited powers over the individual. If they react with skepticism, that could be trouble, because it means they are prepared to accept the idea that the mandate assumes no “limiting principle” over federal power.

“If they are sympathetic to the theory the government lays out for why its powers are not unlimited, that’s a good sign,” Millhiser says. “If they seem very dismissive of it, that’s a bad sign.”