(CBS News) -- 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.
Instead, the four joined forces and crafted a highly unusual, unsigned joint dissent. They deliberately ignored Roberts' decision, the sources said, as if they were no longer even willing to engage with him in debate.
The inner-workings of the Supreme Court are almost impossible to penetrate. The Court's private conferences, when the justices discuss cases and cast their initial votes, include only the nine members - no law clerks or secretaries are permitted. The justices are notoriously close-lipped, and their law clerks must agree to keep matters completely confidential.
But in this closely-watched case, word of Roberts' unusual shift has spread widely within the Court, and is known among law clerks, chambers' aides and secretaries. It also has stirred the ire of the conservative justices, who believed Roberts was standing with them.
After the historic oral arguments in March, the two knowledgeable sources said, Roberts and the four conservatives were poised to strike down at least the individual mandate. There were other issues being argued - severability and the Medicaid extension - but the mandate was the ballgame.
It required individuals to buy insurance or pay a penalty. Congress had never before in the history of the nation ordered Americans to buy a product from a private company as part of its broad powers to regulate commerce. Opponents argued that the law exceeded Congress' power under the Constitution, and an Atlanta-based federal appeals court agreed.
The Atlanta-based federal appeals court said Congress didn't have that kind of expansive power, and it struck down the mandate as unconstitutional.
On this point - Congress' commerce power - Roberts agreed. In the Court's private conference immediately after the arguments, he was aligned with the four conservatives to strike down the mandate.
Roberts was less clear on whether that also meant the rest of the law must fall, the source said. The other four conservatives believed that the mandate could not be lopped off from the rest of the law and that, since one key part was unconstitutional, the entire law must be struck down.
Because Roberts was the most senior justice in the majority to strike down the mandate, he got to choose which justice would write the Court's historic decision. He kept it for himself.
Over the next six weeks, as Roberts began to craft the decision striking down the mandate, the external pressure began to grow. Roberts almost certainly was aware of it.
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.
Some informed observers outside the Court flatly reject the idea that Roberts buckled to liberal pressure, or was stared down by the President. They instead believe that Roberts realized the historical consequences of a ruling striking down the landmark health care law. There was no doctrinal background for the Court to fall back on - nothing in prior Supreme Court cases - to say the individual mandate crossed a constitutional line.
The case raised entirely new issues of power. Never before had Congress tried to force Americans to buy a private product; as a result, never before had the Court ruled Congress lacked that power. It was completely uncharted waters.
To strike down the mandate as exceeding the Commerce Clause, the Court would have to craft a new theory, which could have opened it up to criticism that it reached out to declare the President' health care law unconstitutional.
Roberts was willing to draw that line, but in a way that decided future cases, and not the massive health care case.
Moreover, there are passages in Roberts' opinion that are consistent with his views that unelected judges have assumed too much power over American life, and that courts generally should take a back seat to elected officials, who are closer to the people and can be voted out of office if the people don't like what they're doing.
As Roberts explained in his opinion:
"The framers created a federal government of limited powers, and assigned to this Court the duty of enforcing those limits. The Court does so today. But the Court does not express any opinion on the wisdom of the Affordable Care Act. Under the Constitution, that judgment is reserved to the people."
Regardless of his thinking, it was clear to the conservatives that Roberts wanted the Court out of the red-hot dispute.
Roberts had begun to focus on a different argument to uphold the law and the mandate's penalty by defining it as a tax. That strained argument had received almost no attention in the lower courts, which had uniformly rejected it. It was seen as a long-shot by the law's supporters.
It would have been far easier, legally, for Roberts to have followed the rationale of two conservatives who voted to uphold the law in the lower courts: Appeals Court Judges Laurence Silberman and Jeffrey Sutton.
In separate opinions for the D.C.- and Cincinnati-based federal courts, Silberman and Sutton wrote that the mandate had not exceeded Congress' commerce power.
Roberts surely could have gotten the liberals to join a decision that the mandate was similar to a 1942 Commerce Clause case involving a farmer who was producing wheat for his own use and had no intention of selling it. In that seminal case, the Court ruled the farmer's wheat production nonetheless affected Commerce, and Congress therefore could regulate it.
In the health care case, since no one was urging the Court to overturn that precedent (Wickard v Filburn), the Court could have issued a narrow opinion. It could have ruled that since it wasn't being asked to depart from settled law, the health care act would stand, based on prior precedents.
Instead, Roberts focused the majority opinion on a much more difficult legal proposition: the tax power.
But Roberts also would limit Congress' authority in future cases under the commerce power.
Roberts then engaged in his own lobbying effort - trying to persuade at least Justice Kennedy to join his decision so the Court would appear more united in the case. There was a fair amount of give-and-take with Kennedy and other justices, the sources said. One justice, a source said, described it as "arm-twisting."
Even in Roberts' opinion, which was circulated among the justices in early June, there are phrases that appear tailored to get Kennedy's vote. Roberts even used some of the same language that Kennedy used during oral arguments.
During the arguments in March, Kennedy told Solicitor General Donald Verrilli:
"Here the government is saying that the federal government has a duty to tell the individual citizen that it must act, and that is different from what we have in previous cases - and that changes the relationship of the federal government to the individual in a very fundamental way."
Roberts wrote in the section of his opinion analyzing the Commerce Clause:
"Accepting the government's theory would give Congress the same license to regulate what we do not do, fundamentally changing the relation between the citizen and the federal government."
On the surface, Kennedy would appear to have been Roberts' best shot to persuade. The other three justices - Thomas, Antonin Scalia and Samuel Alito - are seen as more solidly conservative and much less susceptible to pressure.
After all, it was Kennedy who "betrayed" conservatives in 1992, when he flipped his vote in a key abortion case that could have overturned Roe v. Wade, the landmark decision that guaranteed a woman's right to abortion.
In the 1992 case, Planned Parenthood v. Casey, Kennedy initially was with conservatives, but then forged a last-minute alliance with Justices Sandra Day O'Connor and David Souter to put Roe v. Wade on more solid ground than even the original decision itself.
Kennedy has long frustrated conservatives, because he occasionally joins with liberals to provide the key swing vote in cases involving social issues. They openly mock his writing style as grandiose and his jurisprudence as squishy - in other words, changeable and too moderate.
That's not entirely fair to Kennedy. In fact, there are underlying and consistent themes in his jurisprudence, much more so than in the jurisprudence of O'Connor. Kennedy has a libertarian streak, and he is skeptical of expansive government power over individuals. In fact, if there's an issue of an individual versus invasive government, Kennedy sides with the individual.
As a result, Kennedy supports the right to possess a firearm for self-defense AND a woman's right in the context of abortion. He opposes certain laws that discriminate against homosexuals or restrict a person's freedom of speech.
Kennedy also is strong on issues of federalism - and is remarkably consistent. His opinion in a 1999 case, Alden v. Maine, is considered one of the Court's finest in that area. Ruling that states were immune from private lawsuits in state courts, Kennedy wrote: "Sovereign immunity derives not from the Eleventh Amendment but from the federal structure of the original Constitution itself."
And in a 1995 term limits case, when the Court rejected state efforts to impose term limits on Members of Congress, Kennedy wrote a separate, concurring opinion to make a point about federalism:
"Federalism was our nation's own discovery. The framers split the atom of sovereignty . . . It was the genius of their idea that our citizens would have two political capacities, one state and one federal, each protected from incursion by the other."
Those structural boundaries, Kennedy believes, help protect the individual from runaway government power, and are key components to protecting liberty.
All of that dovetails with Kennedy's position on the individual mandate in the health care law. Close associates of Kennedy never thought he would waver in the case once he recognized the federal mandate as an encroachment on individual liberty (points Kennedy later would make in his sections of the joint dissent).
In fact, Kennedy was the most forceful and engaged of all the conservatives in trying to persuade Roberts to stand firm to strike down the mandate. Two sources confirm that he didn't give up until the very end.
But Roberts didn't focus entirely on Kennedy, the sources said. He tried to persuade the conservatives to join at least the parts of his opinion with which they agreed, such as his Commerce Clause analysis.
"People, for good reasons of their own, often fail to do things that would be good for them or good for society. Those failures - joined with the similar failures of others - can readily have a substantial effect on interstate commerce," Roberts wrote in his opinion. "Under the government's logic, that authorizes Congress to use its commerce power to compel citizens to act as the government would have them act.
"That is not the country the framers of our Constitution envision," Roberts wrote.
But despite Roberts' strong language on the Commerce Clause, the conservatives would have none of it, the two sources said, even though there was no significant difference in their reasoning on that issue.
Indeed, since the four conservatives agreed the mandate went beyond the commerce power, the Court now has five Justices who would constrain what Congress can do going forward - imposing significant limits on federal power.
The majority decisions were due on June 1, and the dissenters set about writing a response, due on June 15. The sources say they divided up parts of the opinion, with Kennedy and Scalia doing the bulk of the writing.
The two sources say suggestions that parts of the dissent were originally Roberts' actual majority decision for the Court are inaccurate, and that the dissent was a true joint effort.
The fact that the joint dissent doesn't mention Roberts' majority was not a sign of sloppiness, the sources said, but instead was a signal the conservatives no longer wished to engage in debate with him.
The language in the dissent was sweeping, arguing the Court was overreaching in the name of restraint and ignoring key structural protections in the Constitution. There are clear elements of Scalia - and then, there is Justice Kennedy.
"The fragmentation of power produced by the structure of our government is central to liberty, and when we destroy it, we place liberty in peril," the dissent said. "Today's decision should have vindicated, should have taught, this truth; instead our judgment today has disregarded it."