The Chief Justice position is a "first among equals" title. Its vote counts exactly the same as the other Justices in Court proceedings -- both as to which cases they choose to decide, and as to the decisions themselves. Mr. Roberts' predecessor, Chief Justice Rehnquist, sought to dress up the title with some ceremonial sergeant's stripes on his judicial robe (perhaps his bathrobe, too?), but that has proved to be a short-lived tradition. CJs do tend to define the Courts they serve in the eyes of history, like the Warren Court named after California's former governor, an Eisenhower appointee.
Perhaps that latter distinction gives the Chiefs a particular perspective when it comes to considering the legacies of their Courts, and their personal places in history. Chief Justice Marshall firmly established the principle of judicial review that the Court is the ultimate arbiter of the Constitution's application to act of legislatures, although by so doing his Party lost the early case of Marbury v. Madison. By losing that battle, he won the Court's war to establish itself as a co-equal branch of government. CJ Hughes was one of two Justices whose switch in timeŁ to joining the liberals in upholding New Deal-style legislation, ťsaved The Nine -member Court from FDR's infamous court-packing plan. CJ Warren, too, seems to have recognized the urgent needs of the country in affirming landmark civil rights legislation in the 1960s, morphing from a relatively conservative prosecutor and Governor to a judge so liberal that Ike called his appointment "the biggest dam-fool mistake I ever made."
Generally CJ Roberts is among the four reliable conservatives on the Court. His political credentials are mostly consistent: he clerked for CJ Rehnquist, served in both the Reagan and Bush 1 administrations and was appointed to the Court by Mr. Bush, the younger. Thus, his opinion in the case of ObRomneyCare came as a shock to most, and has been seen as a betrayal by some partisans. A pretty good argument can be made, however, that he was led to that position by his concern for the Court's place in the eyes of the nation. The Supremes do read the newspapers, as the saying goes.
Recently, the Supreme Court has been seen increasingly as just another partisan branch of government, rather than as the impartial Deciders whose loyalty is to the Constitution. Starting with Bush v. Gore and certainly including the wretched Citizens United debacle, the Court's decisions have appeared to many commentators to be evidence that the Justices merely dance with them that brung 'em; the Court splits 5-4 in either direction depending on the current tune called by swingman Justice Kennedy.
In the ObRomneyCare case (okay, Affordable Care Act), Roberts broke with the conservatives and voted to uphold the federal government's right to legislate in the manner it did (back in '09, when it was still in the business of legislating). Thus, he answered those critics, arguably by going where the Constitution led him, instead of imposing a right-of-center reading on it. The fact that he used the feds' taxing power as a basis also allowed him to maintain his conservative credentials by continuing their preference for limiting federal power to act under the authority of the Commerce Clause (for my money, imposing that limit on a health care sector that comprises nearly 20 percent of the economy is absurd, but they framed the issue differently).
Now, it may be that Mr. Roberts believes that ObRomneyCare is bad policy and will fail under its own massive weight, or perhaps he calculated that it is so unpopular that it will contribute to Mr. Romney's election and thus its repeal on the biblically busy First Day of a GOP administration, if so, he was cagey in doing "well" for his side by doing "good" for the Court's reputation -- a bit like CJ Marshall, way back in 1802. Or he may have actually believed that the taxing power is a sufficient basis for upholding the ACA. Some right-side pundits have expressed alarm in the short run (perhaps some of their concern also arises out of long-serving conservative Justice Scalia's increasingly erratic behavior on the bench, his departure could alter the Court's philosophical balance), but this one will be played-out over a longer period, and CJ Roberts'opinion may have been good for both Court and country.
So, happy judicial Independence Day, Mr. Roberts!