Four months ahead of the presidential election, the U.S. Supreme Court on Thursday upheld the crucial part of President Barack Obama's signature health care overhaul in a widely anticipated ruling, putting an end to months of speculations over one of the hottest issues on the campaign trail.

U.S. President Obama speaks in the East Room of the White House in Washington, Thursday, June 28, 2012, after the Supreme Court ruled on his health care legislation. [Agencies]

The Affordable Care Act has been viewed as Obama's chief yet most controversial domestic accomplishment. The Supreme Court decided the overhaul, including its "individual mandate" that virtually requires most Americans to buy health insurance, is constitutional.

Partisans Clash Over Ruling

The passage of the legislation by the then Democrats-controlled Congress in 2010 gained no Republican support and capped decades of debate over pushing forward a national program of health care covering most people. If upheld and implemented, the latest reform is expected to extend health care coverage to about 30 million currently uninsured Americans.

Following the court's morning ruling, both Democrats and Republicans on the campaign trail and in the Congress promptly clashed over health care reform.

President Barack Obama delivered a speech at noon on Thursday, declaring the ruling as "a victory for people all over the country whose lives are more secure because of this law and the Supreme Court's decision to uphold it."

Obama said the Supreme Court's decision upholds the fundamental principle, reaffirming all people in America shall be able to afford quality health care.

Republican presumptive nominee Mitt Romney threw a quick attack over the Affordable Care Act, often dubbed as "Obamacare" by Republicans, saying it's "a bad policy" and "a bad law."

"I will do on my first day if elected president of the United States. And that is I will act to repeal Obamacare," vowed Romney.

His Republican colleagues joined him in vowing to seek a complete repeal of the legislation. Republican House Speaker John Boehner on Thursday also stressed the need to continue to repeal the Obama administration's health care reform.

Like other Democrats seemingly more relieved over the ruling, Democratic Senate Majority Leader Harry Reid said in his tweets now that the matter was settled, "we can work together to create jobs and secure this country's economic future."

Former Democratic Congressman Bart Stupak, who was previously involved in health care issues and the passage of Obama health care legislation during his term in Congress, noted that it is critical for all parties involved in the health care system, including health care stake-holders and the government, to innovate and develop methods to reduce the costs of delivering quality health care and making the insurance expansion affordable for the country.

ELECTION GAME-CHANGER?

The health care plan is a hot issue in the presidential election campaign now getting underway, with Republicans arguing that forcing people into health insurance is unconstitutional, while Democrats argue the mandate could bring down the cost of insurance and offer more Americans access to health insurance. The ruling could have a big impact on the election.

Hundreds of people, including health care stake-holders and activists on both sides, as well as television camera crews, had been awaiting the verdict outside the court.

Four months ahead of November election, both Obama and Romney are also expected to use the high court ruling to push forward their bid to the White House and galvanize voters supporting or opposing the legislation.

However, Obama and Democrats seem to be cautious to declare an early victory over the health care reform and tread more on it in the campaign.

Analysts said whether the ruling will be a game-changer in the 2012 presidential campaign still remains a question.

John Fortier, expert from Bipartisan Policy Center noted that although the high court's decision is momentous, there is still a good chance that there will not be any great political effect weighing on the elections following the ruling.

"Public opinion has remained steady since the fall of 2009, when the health care bill were being debated," he said.

A May Washington Post/ABC joint poll found the health care overhaul, a focus of current news, fell far behind economic recovery and job creation as top issues for voters.

A majority of 52 percent of Americans picked the economy as the most important issue that could impact on their votes. Health care came in second, with only 7 percent of people believing it mattered most.

Ruling Hard To Please

Polls have shown that as a whole the Affordable Care Act still remains unpopular with the public, little changed from two years ago. A Pew Research Center poll last week found that overall more people continue to disapprove than approve of the health care bill by 48 percent versus 43 percent.

More than two years after its passage, the Obama health care bill continues to spark strong feelings from most Americans, particularly among opponents. 35 percent of Americans or 75 percent of the opponents disapprove of the law "very strongly" while 26 percent of Americans or 60 percent of supporters approve of the law "very strongly."

The public preferences tracked down sharply along the party lines. For many partisans, only an "all or nothing" outcome will be acceptable.

Moreover, the "individual mandate", the most controversial part of the law that survived the high court's ruling, has won the least support among Americans. A poll by Kaiser Family Foundation in April found over 30 percent of people were in favor of the " individual mandate," while other provisions of the legislation enjoyed much more favorable ratings.