Read the full statement here.

A sharply divided Supreme Court upheld the individual insurance mandate in President Obama’s health care law on Thursday, handing the White House a major victory on its major domestic achievement four months before the election.

With protestors gathered outside the court's marble halls, Chief Justice John Roberts revealed that he had joined the liberal wing in a 5-4 ruling that the federal government indeed has the power to impose a penalty on those who fail to buy insurance--through its taxing authority, not under the Interstate Commerce Clause, as the administration had argued.

It was a stunning moment because the media and political establishments had essentially concluded after oral arguments that the mandate was toast.

A defeat on that question would have been a stinging setback for a president who staked so much of his political capital on the intractable issue of health care reform but had already lost the debate in the court of public opinion.

In an address from the White House, Obama concentrated on selling the law’s benefits, from parents being able to cover their children under age 26 to some 30 million uninsured people being eligible to get coverage. He gave a major nod to the law’s unpopularity, saying, “It should be pretty clear by now that I didn’t do this because it was good politics.”

The president credited the court with upholding the mandate, saying: “People who can afford health insurance should take responsibility to buy insurance.” And he took a not-so-veiled shot at his opponent, saying such a mandate had once been supported by “the Rpeublican nominee for president.”

Mitt Romney, speaking in front of the Capitol, sided with the court’s dissenters, saying: “If we want to get rid of Obamacare, we have to replace President Obama.”

Rather than arguing with the court’s reasoning, the Republican candidate said that while a majority of the justices found that the health care law “does not violate the Constitution, what they did not do is say Obamacare is good law and good policy.”

Romney ticked off a litany of familiar criticisms of the law as a job-killing budget buster, including the disputed allegation that it could cause 20 million Americans to lose their insurance. But he embraced one central part of the law—that insurance companies not be allowed to reject people for preexisting conditions—that is inextricably tied to the individual mandate that the court upheld.

The case mushroomed into a classic Washington showdown: between competing branches of government, between liberals and conservatives, between highly paid lawyers, between a president defending his signature accomplishment and a challenger who denounced that achievement even though he had passed a similar state measure.

Despite the army of lawmakers, lobbyists, advocates and aides working on the health care battle, the outcome wound up in the hands of nine justices—and in some ways in the hands of a single swing voter, Anthony Kennedy. And while it is not unusual for the judicial branch to serve as the final arbiter on major controversies, John Roberts and the court itself faced the risk that their institution would be seen as overly politicized.

Unlike such fundamental issues as abortion, gay marriage and civil rights, the brawl over the Affordable Care Act turned on a relatively narrow question: Would the federal government overstep its constitutional bounds by ordering people to buy insurance or pay a stiff fine? Beyond that, the justices also had to weigh whether an expansion of the federal-state Medicaid program amounted to coercion. The ruling says the feds can indeed pump more money into the program but cannot force states to go along, since they bear part of the financial burden.

Health care consumed much of the president’s first term, and he managed the rare political feat of losing by winning. After the health care bill was demonized by Republicans, some of whom had supported such provisions as an individual mandate in the past, the president muscled the bill through on a party-line maneuver even after Ted Kennedy’s death deprived him of a 60^th Senate vote.

But in accomplishing what every Democratic president since Harry Truman had failed to do, Obama got shellacked in the messaging war, with the law more unpopular now than the day it was passed. Still, Democrats were supremely confident that the law would withstand constitutional challenge—the latest in a series of miscalculations that permeated the debate.

Thus it was that Mitt Romney, who passed a similar version of health care reform as governor of Massachusetts, became one of Obamacare’s leading critics, even as his GOP primary opponents tried to tar him with the same brush.

Now both Obama and Romney face a very different campaign landscape in the wake of the ruling. Obama can tout the law's benefits, having dodged a legal disaster, while Romney can resume his attacks on a law despised on the right--though his leverage is undercut  by his particular history on health care.

The ruling also highlights an often-overshadowed question in presidential contests: which candidate gets to fill Supreme Court vacancies over the next four years.