WASHINGTON (AP) --The Supreme Court's decision to uphold President Barack Obama's sweeping federal health care law handed the Democratic incumbent crucial election-year vindication for his signature legislative accomplishment. Republican rival Mitt Romney said he would repeal the overhaul on his first day in office, if elected.
"If we want to get rid of Obamacare, we're going to have to replace President Obama," Romney said from a rooftop in Washington overlooking the U.S. Capitol.
Romney spoke shortly before Obama was to address the court's decision from the White House.
The high court ruling put an end to what had been one of the biggest unknowns in the presidential race. Four months from Election Day, both Obama and Romney will seek to use the high court ruling to bolster their vision for the country, as well as raise money for their campaigns.
The Romney campaign said it had collected more than $300,000 in online donations in the hours after the decision was announced.
The high court announced Thursday, in a 5-4 decision, that it was upholding the requirement at the heart of the health care law: that most individuals must buy health insurance or pay a penalty.
The decision means the historic overhaul will continue to go into effect over the next several years, affecting the way people receive and pay for personal medical care. The ruling also handed Obama a campaign-season victory in rejecting arguments that Congress went too far in requiring most Americans to have health insurance.
The Obama and Romney campaigns have been quietly preparing for months how they would respond to the ruling.
While the White House publically expressed confidence that the overhaul would be upheld, Obama aides feared the political ramifications for the president if the law were to be overturned.
Some Romney aides believe the court's decision could energize Republican voters and prove to be politically positive for the presumptive GOP nominee. Romney on Thursday doubled-down on his campaign pledge to repeal the law and cast his candidacy as the next best hope for the millions of Americans who oppose the overhaul.
Republican National Committee Chairman Reince Priebus also said the decision sets the stakes for the Nov. 6 election.
"Now, the only way to save the country from Obamacare's budget-busting government takeover of health care is to elect a new president," Priebus said.
The court's ruling will have a far-reaching impact on the nation's health care system. About 30 million of the 50 million uninsured Americans would get coverage in 2014 when a big expansion begins.
Polling suggests that most Americans oppose the law, but an overwhelming majority want Congress and the president to find a new remedy if it's struck down.
The court's announcement was expected to be followed almost immediately by a barrage of advertisements and fundraising appeals from Democrats and Republicans all trying to cast the decision in the most advantageous light for their candidates.
Obama's campaign began trying to raise money off the ruling even before it was announced. In a Thursday morning fundraising email with the subject line "Today's Decision," Obama campaign manager Jim Messina told supporters "no matter what, today is an important day to have Barack Obama's back."
Outside groups also are ready to unleash a flood of advertising, including a 16-state, $7 million ad buy from the conservative political action group Americans for Prosperity.
AP White House Correspondent Ben Feller contributed to this report.