Editor's note: Jeffrey Toobin is a CNN senior legal analyst and a staff writer at The New Yorker. A former assistant U.S. attorney, Toobin is the author of several critically acclaimed best-sellers, including "The Nine: Inside the Secret World of the Supreme Court" and "Too Close to Call: The Thirty-Six-Day Battle to Decide the 2000 Election."
(CNN) -- Chief Justice John G. Roberts Jr. is fond of pointing out the original reason that judges came to wear black robes. It's to make them look alike, to minimize the differences between the individuals who occupy the role and to suggest that the law will be applied even-handedly, no matter who happens to be dressed in black.
Well, that may be the theory, but the events of the last few weeks show that the Supreme Court is riven by the same partisan divisions as the rest of Washington -- and it's likely to get even more heated sooner rather than later.
The latest round started January 21, when a bitterly divided court issued its decision in the Citizens United case. The 5-4 ruling decreed that corporations enjoy the same rights as individuals to free speech under the First Amendment, and it gave corporations (and labor unions) the right to spend unlimited funds on political advertising right up until Election Day.
The political effect of, if not motivation for, the decision was clear: Citizens United looks to be a big win for Republicans, who are the likely beneficiaries of the newly lubricated corporate largesse.
President Obama struck back just six days later, during his State of the Union address, which he used to make an unusually pointed attack on the court's decision. With a majority of the court seated right in front of him, Obama said the ruling opened the door even to foreign companies meddling in the American political system.
With the cameras rolling, Justice Samuel A. Alito Jr. grimaced and muttered "not true" in response to the president. (Check out the video .) In fact, Citizens United is intentionally ambiguous on its effect on foreign corporations -- so it's not clear whether Obama or Alito is right -- but the open confrontation between the two men suggests the intensity of their split. (That then-Sen. Obama voted against Alito's confirmation suggests the origin of the animosity.)
Last week, Roberts himself weighed in, denouncing the State of the Union as a "political pep rally" and weighing a future boycott of the proceedings by the justices.
In fact, several justices (including Roberts' predecessor, William H. Rehnquist) have avoided the State of the Union for years, for just the reason Roberts suggested: that it's too bound up in contemporary politics. But the fact that Roberts only came to object now -- and not during the presidency of George W. Bush, who appointed him -- suggests that it's Democrats, not noisy democracy, that's really bothering the chief justice.
There's no doubt what's bothering Ginni Thomas, the wife of Justice Clarence Thomas. A veteran Republican activist, she just announced plans to start an online Tea Party advocacy group, which may be funded, in part, by the corporate donations newly freed up by the Citizens United decision.
All of this controversy may come to a head soon, because Justice John Paul Stevens, the court's senior associate justice and the leader of its liberal wing, is likely to resign this spring. In an interview for The New Yorker, Stevens told me that he will probably decide in less than a month whether he will retire. With his 90th birthday looming in April, Stevens gave me every indication that he will leave the court , which will set up a confirmation battle over Obama's appointment of his successor.
Appointed by President Gerald R. Ford in 1975, Stevens represented a moderate Republican tradition that has had deep roots on the court and in broader American life. But just as Stevens represents the last of his political breed on the court, so, too, have moderates largely disappeared from the contemporary GOP as a whole.
In all likelihood, Obama will name a Democrat to replace him. (Solicitor General Elena Kagan appears to be the leading candidate.) So without Stevens, the court will look like the Capitol, across First Street, from its own marble palace; both will be places where Democrats and Republicans fight.
In a way, all of this controversy at the court provides a bracing civics lesson. The justices deal with the most volatile issues in American life, from abortion to the war on terror. It is folly to pretend that the court could figure out a way to deal with these issues in an objective or nonpolitical way. The justices reach answers to the questions before them based on their judicial philosophies, which are nearly indistinguishable from their political views. This is not new. The divisions in the court have always reflected the political divisions in the country, but never more so than today.
The opinions expressed in this commentary are solely those of Jeffrey Toobin.