(CBS News) -- In a historic decision, the Supreme Court on Thursday upheld the critical piece of President Obama's Affordable Care Act, the individual mandate.
By upholding the individual mandate -- the requirement for all Americans to acquire health insurance -- the court kept what many described as the "heart" of the law. The decision creates some certainty surrounding federal health care policy, allowing federal and state rulemakers to, for now, implement the law.
READ: The Supreme Court's decision (PDF)
The decision was five to four, with Chief Justice John Roberts siding with the liberal justices and writing the majority opinion.
The court found fault with one major provision of the law, which would have expanded Medicaid coverage. Currently, Medicaid is a joint federal-state program that provides health care to certain poor Americans, such as children and the elderly. In 2014, the Affordable Care Act would have opened up Medicaid to anyone with an income under 138 percent of the federal poverty line.
Several states argued the expansion of the program would have placed an undue burden on the states, and the court agreed, writing in its opinion that the provision was like a "gun to the head of the states." If a state had chosen not to expand the program as the law required, it would have had to opt out of Medicaid completely -- something no state could afford to do.
The high court's move hardly ends the political controversy surrounding the law; if anything, the decision to uphold most of the law is sure to renew calls for lawmakers to repeal the Affordable Care Act legislatively.
A political victory for Obama
The Supreme Court's decision to uphold President Barack Obama's sweeping health care law is a crucial election-year victory for the Democratic incumbent.
It also marks a pivotal point in the presidential race.
For Obama, the decision vindicates his most significant legislative accomplishment.
Republican challenger Mitt Romney opposes the health care overhaul and is expected to double-down on his campaign pledge to repeal the law if he is elected.
The high court announced Thursday that it was upholding the individual insurance requirement at the heart of the health care overhaul.
Boehner: Health ruling shows need to repeal law
House Speaker John Boehner says the Supreme Court ruling upholding the individual insurance requirement at the heart of President Barack Obama's health care overhaul shows the need to repeal the law.
The Ohio Republican says in a statement that the law is hurting the economy by increasing health care costs and making it difficult for small businesses to hire.
He says the court's ruling demands repeal of the entire law.
Boehner say Americans want a common-sense approach to health care. He says Republicans are ready to work with a president who's willing to listen to the people and "will not repeat the mistakes that gave our country 'Obamacare.'"
Romney looks to use ruling to his advantage
President Obama and Mitt Romney are both gearing up to use today's Supreme Court decision on health care for political gain.
Romney, an opponent of the law, is planning to cast himself as the best hope for millions of Americans who favor the law's repeal.
His campaign says in the hour after the decision was announced, it collected more than $100,000 in online donations.
Romney is expected to speak about the decision today, as is Obama.
Republican Party chairman Reince Priebus says today's decision sets the stakes for the November election. He says only the election of a new president will save the country from what he calls "Obamacare's budget-busting government takeover of health care."
But Democrats say Romney -- who backed an individual health insurance mandate when he was Massachusetts governor -- will have a hard time exploiting the ruling. Democratic consultant Jim Manley calls Romney "the intellectual godfather of Obamacare."
Ruling brings emotional response from both sides
The ruling inspired emotional responses from both liberals and conservatives across the country, illustrating how politically explosive the issue is.
Upon learning the news, House Democratic Leader Nancy Pelosi first left messages for the president and the vice president, according to a top Pelosi aide. Then she called Vicki Kennedy, the wife of the late senator and health care reform champion Ted Kennedy. "Now, Teddy can rest," Pelosi told Kennedy.
The Democratic leader -- wearing her lucky purple pumps -- called her husband after that and then celebrated with her staff.
On the steps of the Supreme Court, before it was clear what the ruling was, Tea Partiers and other opponents of the law cheered and waved signs, initially thinking the law was struck down. The cheered, "Constitution wins!" A few minutes later, after the news was cleared up, they started chanting, "this is not over," and "repeal it now."
Supporters of the health care law, meanwhile, danced in front of the court and shouted, "Yes we can! Yes we can!"
Meka Sales, a public health professional from Charlotte, N.C., told CBS News that at a meeting of the American Public Health Association there, people were crying tears of happiness when they heard the news.
"We were totally unprepared for such a favorable decision. I think tears were on deck for a disappointment but what an incredible surprise," she said. "The room was filled with complete joy and a sense of justice for those that will have access to health care in the future."
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