By Patricia Zengerle and Jeff Mason
WASHINGTON (Reuters) - As Democrats celebrated the U.S. Supreme Court's ruling on Thursday that saved President Barack Obama's sweeping healthcare overhaul, the mood inside the White House was a subdued satisfaction.
There were hugs and handshakes after Obama learned of the ruling from White House counsel Kathy Ruemmler, but also a realization: Thursday's victory in court could energize Republicans who oppose the law and leave Obama with a tougher fight for a second four-year term in the White House.
The survival of the law - dubbed "Obamacare" by critics - preserves one of the Republicans' favorite tools for bashing the president as he vies for re-election on November 6 against Mitt Romney, who vowed again on Thursday to press for the repeal of the measure if he is elected.
Polls suggest that Republicans have won the public relations battle over the 2010 law. A majority of Americans say they oppose the law, but when asked about many of its provisions, most support them.
About two hours after the court's ruling on Thursday, Obama made clear that in the four-plus months remaining before the election, he is determined to do a better job of convincing Americans of the law's merits than Democrats have done so far.
He did so in a setting that was reminder of one of his administration's greatest successes. Speaking in the East Room of the White House - the same setting he used to announce the death of al Qaeda leader Osama bin Laden last year - Obama, point by point, reminded middle-class Americans of how they have begun to benefit from the healthcare law.
"It should be pretty clear by now that I didn't do this because it was good politics. I did it because I believed it was good for the country. I did it because I believed it was good for the American people," Obama said of a law passed despite unified Republican opposition at a time when his fellow Democrats controlled both chambers of Congress.
Obama started by reassuring Americans who already have insurance that they will keep it. "This law will only make it more secure and more affordable," Obama said.
He listed popular provisions, reminding Americans that children can stay on their parents' insurance until they are 26, older Americans get a discount on prescription drugs and insurance companies must provide free preventive care.
And he defended the "individual mandate," forcing most Americans to obtain health insurance by 2014 or face a penalty, as a requirement that "people who can afford health insurance should take the responsibility to buy health insurance."
Some analysts said that if the president and his team had been so clear all along in detailing the bill's merits in the face of Republican criticism, the law might be more popular.
"Obama did his best job ever explaining just how it affects people," said Thomas Mann of the Brookings Institution think tank.
PRESSURE ON THE PRESIDENT
Even his supporters say the pressure is on Obama to keep making the case for the law.
"Too few people to this day understand the benefits," Representative Steve Israel, chairman of the Democratic Congressional Campaign Committee, said at this week's Reuters Washington Summit. "That reflects a focus on policy, which was appropriate, to the detriment of the message, which is still hurting us."
In a 5-4 ruling, the Supreme Court preserved the individual mandate, the most contentious provision in a law seen as Obama's signature domestic policy achievement. The court also preserved, with some changes, a provision of the law expanding the Medicaid health insurance program for the poor.
The decision "really helps Obama, and the Democrats will ride that hard," said James Morone, who specializes in politics and healthcare at Brown University in Rhode Island. Romney "will be fighting out from under that for the rest of the campaign."
The decision heightens a clear contrast in the campaign between Obama and Romney. Obama can say he has fulfilled a promise he made while running in 2008 and tell Americans that victory is at risk if Romney replaces him.
The ruling also helps Obama's efforts to cast Romney and the Republicans as uncaring and unconcerned about health insurance coverage for Americans.
The ruling also could help dampen criticism that Obama had focused on pushing a potentially unconstitutional healthcare law rather than job creation in 2009 and early 2010 as the United States struggled to emerge from economic recession.
"Obama can say, 'I didn't waste the first year of my presidency, even though I'm accused of ignoring the economy. I did something of a long-term benefit to the country,'" said Ethan Siegel, an analyst at The Washington Exchange, which tracks political developments for investors, at the Reuters summit.
Republicans said Romney will make attacks on the law - and especially the individual mandate - a feature of his campaign. Opposition to the law helped inspire victories for Republicans in the 2010 congressional elections when they won a majority in the House of Representatives and statehouses across the country.
"This is a weapon that Romney can certainly use if he spins it the right way," Republican strategist Ford O'Connell said. "He can say, 'If you want this law repealed, I am literally your last option.'"
Democrats celebrated the court's ruling. Nancy Pelosi, the top House Democrat, wore her lucky purple shoes on Thursday - the same pair she wore when the law was passed in March 2010 when she was House speaker.
A Democratic aide related this exchange between Pelosi and Representative George Miller, another Democrat:
"What a great victory," Pelosi said.
"You bet your ass," Miller responded, to which Pelosi replied, laughing: "I did."
(Additional reporting by Alina Selyukh and Donna Smith; Editing by David Lindsey and Will Dunham)