CBS News is reporting that Chief Justice John Roberts, a Republican appointee who sided with the Supreme Court's liberal voting block in voting to uphold President Obama's health care law, switched his vote after initially coming down against the law's individual mandate:

Chief Justice John Roberts initially sided with the Supreme Court's four conservative justices to strike down the heart of President Obama's health care reform law, the Affordable Care Act, but later changed his position and formed an alliance with liberals to uphold the bulk of the law, according to two sources with specific knowledge of the deliberations.

Roberts then withstood a month-long, desperate campaign to bring him back to his original position, the sources said. Ironically, Justice Anthony Kennedy - believed by many conservatives to be the justice most likely to defect and vote for the law - led the effort to try to bring Roberts back to the fold.

"He was relentless," one source said of Kennedy's efforts. "He was very engaged in this."

But this time, Roberts held firm. And so the conservatives handed him their own message which, as one justice put it, essentially translated into, "You're on your own."

The conservatives refused to join any aspect of his opinion, including sections with which they agreed, such as his analysis imposing limits on Congress' power under the Commerce Clause, the sources said.

Why did Roberts switch? The article says that no one knows for sure, but speculates that pressure from liberal editorialists and others who warned that the high court's reputation would be ruined if it struck down the law might have made Roberts reverse his initial position:

Some of the conservatives, such as Justice Clarence Thomas, deliberately avoid news articles on the Court when issues are pending (and avoid some publications altogether, such as The New York Times). They've explained that they don't want to be influenced by outside opinion or feel pressure from outlets that are perceived as liberal.

But Roberts pays attention to media coverage. As Chief Justice, he is keenly aware of his leadership role on the Court, and he also is sensitive to how the Court is perceived by the public.

There were countless news articles in May warning of damage to the Court - and to Roberts' reputation - if the Court were to strike down the mandate. Leading politicians, including the President himself, had expressed confidence the mandate would be upheld.

Some even suggested that if Roberts struck down the mandate, it would prove he had been deceitful during his confirmation hearings, when he explained a philosophy of judicial restraint.

It was around this time that it also became clear to the conservative justices that Roberts was, as one put it, "wobbly," the sources said.

It is not known why Roberts changed his view on the mandate and decided to uphold the law. At least one conservative justice tried to get him to explain it, but was unsatisfied with the response, according to a source with knowledge of the conversation.

At the legal blog the Volokh Conspiracy, Stewart Baker notes that Senator Patrick Leahy, the Democratic Chairman of the Senate Judiciary Committee, gave an unusual and "weirdly belated" speech urging Roberts to vote in favor of the law—weird because the initial votes on the case had already been cast. Those types of speeches, Baker notes, are usually a bad idea, or at least a gamble, because of the possibility that they will backfire. So why did the senior Democrat on the Senate's judicial committee make such an unusual gamble right around the time that Roberts is now said to have "gone wobbly" and changed his vote? Were there leaks from within about Roberts' wariness that went only to one side of the aisle?

The existence of the CBS story, which reporter Jan Crawford says is sourced to two court insiders (possibly even current justices), is amazing enough on its own. But if the story and its speculation about the reasons behind Roberts' switch are true, then the implications are downright shocking: Essentially, it would mean that the Chief Justice of the Supreme Court was bullied into changing his position, and the ultimate outcome, on perhaps the most consequential Supreme Court case in the last several decades, because prominent Democrats and liberals threatened to throw a temper tantrum if he didn't vote the way they wanted.