The indelible Supreme Court moment of 2010 took place across the street at the U.S. Capitol on Jan. 27.

In his State of the Union address, President Barack Obama scolded the Court for its Citizens United decision the week before. Democratic members of Congress stood and applauded, glaring at the justices who sat expressionless — except for Justice Samuel Alito Jr., who mouthed the words “not true” as he gave the silent headshake heard ’round the world.

Not since Franklin Delano Roosevelt dinged the judiciary in his 1937 run-up to the court-packing plan had a president criticized the Court in such a high-profile forum. The three branches of government, accustomed to insulting each other from afar in written briefs and opinions, were suddenly duking it out in person. The episode framed the Court’s entire year, even overshadowing the departure of Justice John Paul Stevens and the confirmation of Elena Kagan to replace him.

For Democrats, the flap over Citizens United v. Federal Election Commission was a Kodak moment showing the Court as a captive of corporate interests. Not only had the Court lifted restraints on corporate spending in elections, but the conservative majority unabashedly reached out to make the ruling that broad, when it could have decided it more narrowly.

“It confirmed the dominant impression of the Court as closely aligned with the agenda of corporate America, and what Alito did showed just how passionate the justices are on that side,” said American University Washington College of Law professor Jamie Raskin, also a senior fellow at the liberal People for the American Way.

As further evidence, Raskin points to the decisions in Skilling v. U.S., Black v. U.S. and Weyhrauch v. U.S. later in the term, narrowing the “honest services” fraud statute used to nab white-collar criminals. “I happen to think the decisions were correct. There is a fatal ambiguity in the law,” said Raskin. “But it comes from a Court that systematically rejects the claims of defendants who are not in the white-collar category.”

To Raskin, Citizens United and its aftermath served as a bookend for the Court’s activist, conservative-dominated decade. “It began with Bush v. Gore deciding one election, and ended with Citizens United effectively deciding all of them,” Raskin said.

But even if that is the impression the decision left on the public, will it stick? A populace that can’t name more than one or two justices can’t be expected to retain the details of a complex campaign-finance decision.

Stanford Law School professor Michael McConnell thinks the Citizens United decision was not such a defining moment. “It was an instance of overreach, but I don’t think it was incorrectly decided,” said McConnell, a former judge on the U.S. Court of Appeals for the 10th Circuit appointed by President George W. Bush. The strong reaction to the ruling, McConnell said, “was less about the Court and less about the decision than it was about political posturing.” Whatever bad feelings about it remain McConnell sees as a something of a self-inflicted wound. “By reaching out to decide it so broadly, the Court made it far more controversial than it had to be.”

In the fifth year of the Roberts Court, did Citizens United signal an activist march to the right? McConnell does not think so, pointing to decisions like 2009′s Northwest Austin Municipal Utility District No. 1 v. Holder, which deliberately stopped short of deciding whether a section of the Voting Rights Act was unconstitutional. Even McDonald v. Chicago, which applied the Second Amendment right to bear arms against state and local firearms regulation, was an example of restraint, McConnell said, because the Court used the traditional due process clause rationale rather than the more exotic privileges or immunities clause.

Elena Kagan’s ascension to the Court — the other moment when the Court flickered in the public consciousness in 2010 — may not alter the Roberts Court’s direction, at least in the short term. She may even be significantly more moderate in votes and inclination than Stevens turned out to be in his later years on the Court.

“The Court hasn’t had a strong intellectually grounded middle in a long time,” McConnell said. “My hope is that she will reinvigorate a center on the Court.” Her role as a dean of Harvard Law School who united a politically divide faculty points to that potential role, McConnell said. “But we probably won’t know for sure for 10 years.”

Raskin agreed: “She has enormous political skills, and that counts for something on the Court.” But where she will land on the ideological spectrum is unclear. From her background, Raskin said, “I don’t think she will fill the shoes of a Thurgood Marshall or a Bill Brennan. She is someone who constantly searches for a centrist common ground. That may be just what the liberals need right now.”

During the confirmation process, Republicans grumbled about her lack of judicial experience, but she prevailed in early August with a 63-37 Senate confirmation vote. She hewed a middle course in her statements before the Senate Judiciary Committee. Asked about Chief Justice John Roberts Jr.’s famous analogy between judges and umpires calling calls and strikes, Kagan said he was “correct in important respects,” but gave the incorrect impression that judging is a “robotic enterprise.”

As the year ended, Kagan had no chance to show whether she was an umpire or unrobotic. She took a hard line on recusals, bowing out of roughly half the Court’s argued cases because she had, as solicitor general, either taken a position or merely reviewed the briefs. In the one major business case the Court decided before the end of the year, Costco Wholesale Corp. v. Omega S.A., a copyright case, her recusal triggered a 4-4 tie.

Judicial ethics were a background concern in another unusual piece of Supreme Court news this year. Justice Clarence Thomas’s wife Virginia launched a conservative advocacy group called Liberty Central just as the Tea Party movement was beginning to play a significant role in electoral politics. She had formerly been an official of the conservative Heritage Foundation, so her political leanings were no surprise. But because her new group was taking donations from unnamed sources, and taking stands on issues that could come before the high court, her new role caused controversy.

The spotlight on Virginia Thomas intensified in October when it was reported that she had left a phone message for Anita Hill, the law professor who had, 19 years ago, accused Justice Thomas of sexually harassing her. She urged Hill to apologize, but Hill declined. By year’s end, Virginia Thomas stepped back from her leadership role at Liberty Central and said the phone call was probably a bad idea.

Heading into 2011, the Court will soon be handing down big decisions on free speech and class actions, and the voguish issue of pre-emption. But because of what happened last January, much of the suspense will focus on how many black-robed justices show up for Obama’s 2011 State of the Union address.

Roberts, Alito and Scalia have already signaled they may have other plans that night, with Scalia calling it a “juvenile spectacle” and Alito disdaining the “ potted plant” role justices are supposed to play. Justice Ruth Bader Ginsburg plans to attend as she usually does, to show America that the Court includes women. And Justice Stephen Breyer will be there, too, to remind the world there’s a third branch of government.

The question mark is whether any appointees of Republican presidents will attend, said McConnell, who hopes it won’t be a “political football” again. As with everything else at the Supreme Court, Justice Anthony Kennedy may be the swing vote, who shows whether the justices, like members of Congress, can sometimes cross the aisle.

Tony Mauro can be contacted at tmauro@alm.com.