WASHINGTON -- The Supreme Court has upheld the individual insurance requirement at the heart of President Barack Obama's health care overhaul.
The court on Thursday handed Obama a major campaign-season victory in rejecting arguments that Congress went too far in requiring most Americans to have health insurance or pay a penalty.
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Basically, a bare majority of the justices said that the individual mandate -- the requirement that most Americans buy health insurance or pay a fine -- is constitutional as a tax.
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Chief Justice John Roberts -- a conservative appointed by President George W. Bush -- provided a key vote to preserve the landmark health care law, which figures to be a major issue in Obama's re-election bid against Republican opponent Mitt Romney.
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The justices decided the tax question on a 5-4 vote, with four Republican appointees in dissent: Anthony Kennedy, Antonin Scalia, Clarence Thomas, and Samuel Alito.
Roberts, also a GOP appointee, joined four Democratic appointees in upholding the mandate: Ruth Bader Ginsburg, Stephen Breyer, Sonia Sotomayor, and Elena Kagan. Obama appointed justices Sotomayor and Kagan.
The announcement will have a major impact on the nation's health care system, the actions of both federal and state governments, and the course of the November presidential and congressional elections.
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As lawyers examined the details of the various opinions, political analysts quickly predicted at least a short-term political boost for Obama.
Peter A. Brown, assistant director of the Quinnipiac University Polling Institute, said "You can hear the sigh of relief at the White House" over a big plus for Obama.
"It allows the president's signature achievement to stand," Brown said. "Since politics is the ultimate zero-sum game, what's good for Obama is bad for Gov. Mitt Romney."
Republican Mitt Romney is promising that he will repeal the federal health care law the Supreme Court just upheld.
He called the decision incorrect and said Thursday that it is "bad law." He says it raises taxes and cuts Medicare.
Romney says that, if elected in November, he will work to repeal and replace the law. But he hasn't said precisely how.
As Massachusetts governor, Romney signed into law a measure that required all state residents to have health coverage.
Brown also noted that the ruling allows the Republican "to continue campaigning against the law and promising to repeal it."
The Republican-controlled House will vote July 11 for a full repeal of the health care law. It is a symbolic move that stands no chance of passage in the Democratic controlled Senate. House Budget Chairman Paul Ryan, R-Wis., acknowledged that the election will be a determining factor for the law's fate and the GOP's ability to overturn it. "It's up to the American people in the next election and their representatives to determine the fate of this law," he said.
Other congressional Republicans vowed to step up efforts to repeal what they call "Obamacare," should they win control of Congress in the November elections.
"The president's health care law is hurting our economy by driving up health costs and making it harder for small businesses to hire," said House Speaker John Boehner, R-Ohio. "Today's ruling underscores the urgency of repealing this harmful law in its entirety."
Conservative groups plan to launch major advertising efforts to attack the law. American For Prosperity, which already has spent $12 million to criticize Obama's energy policies, plans an $8.2 million ad blitz in response to the ruling.
The ads will run in a dozen key presidential battleground states: Colorado, Florida, Iowa, Minnesota, Nevada, New Hampshire, New Mexico, North Carolina, Ohio, Pennsylvania, Virginia, Wisconsin.
"Americans for Prosperity is deeply disappointed by the Supreme Court's decision to uphold a law that most Americans believed to be unconstitutional and wanted to see repealed," the group's president Tim Phillips said in statement. "As a result, unless Congress steps in and repeals this legislation, health care costs for most Americans will go up while the quality of health care goes down as Washington politicians ramp up yet another massive new bureaucracy. The Court got it wrong, and now Congress must step in."
The law's individual mandate had been the key question for the court.
Critics called the requirement an unconstitutional overreach by Congress and the Obama administration; supporters say it is necessary to finance the health care plan.
The decision showed once again that the high court isn't shy about weighing in on major legislative issues and influencing the political balance of power. Since its 5-4 decision affirming George W. Bush's election as president in December 2000, the justices have tackled issues of huge importance, ranging from affirmative action to campaign finance, with equal aplomb.
In this case, the decision will have an immediate and major impact on the nation's health care system, the actions of both federal and state governments, the course of the November elections for president and Congress, and the reputation of the Supreme Court for decades to come.
While the individual mandate requiring most Americans to have health insurance remained 18 months away from implementation, many other provisions already have gone into effect, such as reductions in seniors' prescription drug costs, help for children and some adults with pre-existing conditions, and allowing children up to age 26 to remain on their parents' policies.
Stocks of hospital companies are moving sharply higher after initial reports said the Supreme Court upheld the individual insurance requirement in President Barack Obama's health care overhaul.
HCA Holdings stock is up 10 percent. Community Health Systems is also up 10 percent.
Stocks of drug companies and medical device makers are slightly lower for the day as analysts sort through the Supreme Court's ruling. Stocks of the biggest insurance companies are also lower.
Our initial bulletin erroneously said the measure was struck down; we apologize for the error.
(The Associated Press and USA Today contributed to this report)