( CNN ) -- When the Supreme Court hears an extraordinary three days of arguments this week about the constitutionality of the Affordable Care Act , thousands of words will pass between the justices and the lawyers appearing before them . Still , it 's likely that the single most important word in the case will never be uttered in the courtroom : . Obama . The Supreme Court can make or break presidencies . Almost a dozen years ago , five justices thrust George W. Bush into the Oval Office . A generation earlier , in United States v. Nixon , a unanimous court effectively ended the presidency of Richard M. Nixon by ordering him to provide the Watergate special prosecutor with the White House tapes . Now , to a great extent , the court will render a verdict on the current president 's first term . The Supreme Court and election year blockbusters . The stakes for Barack Obama can hardly be overstated , both substantively and politically . Health insurance for 30 million citizens hangs in the balance in this case . Obama took on the challenge that had defeated every Democratic president since Lyndon Johnson -- how to expand access to health care for millions of citizens who did n't have it . Obama won a brutal battle to get the Patient Protection and Affordable Care Act through Congress , but it will matter little if the court invalidates the law . Obama is also , of course , a candidate for re-election , and a defeat in the Supreme Court would be a disaster for his chances to win again . If the court strikes down the law , the Republican candidate , presumably Mitt Romney , could say that the Supreme Court proved his own point -- that the incumbent is an out-of-the-mainstream liberal . And Romney could add that his own health care plan , for all its similarities to Obamacare , passed muster in the courts . Read a transcript of Monday 's court arguments . For any president or any politician , losing is never good politics -- and a Supreme Court defeat would mark Obama as a loser in a significant and dramatic way . The specifics of the case are complex : What is the scope of the commerce clause of Article I of the Constitution ? When is a challenge to a federal law premature ? How does a court separate challenges to specific provisions of a law from a claim that an entire law is unconstitutional ? But the larger issue in the case reflects a fundamental division in American politics that has persisted for generations : What is the role of the federal government ? Obama is heir to a political tradition of activist government , which asserts that the people can rely on programs that protect them from life 's misfortunes . The alternative tradition is based on libertarian principles , which hold that government interference in private markets generally does more harm than good . What makes this case so extraordinary is that this debate , as a constitutional matter , looked settled for decades . After Franklin D. Roosevelt made nine appointments to the court during his long tenure in the White House , the Supreme Court embraced a broad conception of government power , especially when it comes to regulating the national economy . Constitutional challenges to government power became rare , and successful ones rarer still . The commerce clause became , in effect , a blank check for Congress . But elections have consequences , and conservative presidents have appointed conservative judges , especially to the Supreme Court . Throughout the'70s , '80s and '90s , moderate Republicans such as Lewis Powell and Sandra Day O'Connor reflected the modern consensus that allowed a vibrant government role in the national economy . But moderate Republicans are disappearing , including on the Supreme Court . Chief Justice John Roberts and Samuel Alito reflect the modern conservatism of the man who appointed them , George W. Bush . The legal approach of Clarence Thomas advanced the tea party agenda before the name even existed . Antonin Scalia has defined judicial conservatism for a generation . That 's four votes right there . Four Democrats -- Ruth Bader Ginsburg , Stephen Breyer , Sonia Sotomayor and Elena Kagan -- can be counted on to embrace the post-FDR model of government involvement in the economy . As always , that could leave the case in the hands of Anthony Kennedy , the swing vote . The outcome is uncertain , even if the stakes are not . The language will be arcane , sometimes nearly incomprehensible to nonspecialists . The subject will be principles , not personalities . And so those of us in the courtroom might never hear the name of the man with the biggest stake in the outcome . The opinions expressed in this commentary are solely those of Jeffrey Toobin .
Toobin : Post-FDR hears challenge on health reform ; high stakes for Obama . He says defeat would mark U.S. as a loser ; would be bad news in today . He says details of challenge complex ; real issue dividing U.S. : What is government 's role ? Toobin : Post-FDR court backed more activist government . Not so an election year ; outcome uncertain .