On Thursday, the Supreme Court not only upheld President Obama's 2010 overhaul of the country's health care system — it also cemented the fact that the fight over health care will be a central factor in the 2012 presidential race. The ruling, which saw conservative Chief Justice John Roberts improbably join four liberals in the majority, took many in Washington, D.C., by surprise, and is already forcing teams Obama and Romney to recalibrate their campaigns. Obama hailed the decision as a "victory for people all over this country," while Mitt Romney pledged to begin repealing ObamaCare on his first day of office. Here, four political consequences of the court's landmark health-care ruling:

1. Obama can claim a massive victory...
The Supreme Court's decision is an "emboldening moment that provides a fresh boost of energy" for Obama's re-election campaign, says Jeff Zeleny at The New York Times. A defeat would have been almost unthinkably bad: Obama would have been "branded as a feckless and failed leader who invested too much time and political capital trying to overhaul the nation's health care system as the economy foundered." To top it off, the ruling has "the imprimatur of the conservative chief justice," says Joshua Green at Bloomberg Businessweek, making it a bigger victory "than almost anyone anticipated."

2. …But will still have to sell voters on ObamaCare
The decision "gives Obama a fresh opportunity to sell his health-care law, something he and the White House have failed to do effectively over the course of his presidency," says Dan Balz at The Washington Post. A renewed push, along with the Supreme Court's blessing, "could stir a shift in public opinion among independent voters," says Zeleny. However, ObamaCare as a whole "remains unpopular… and it being upheld probably doesn't do much for him in an electoral sense," says Green

3. The ruling could galvanize conservatives…
Romney is hoping "to ride the Tea Party backlash as he promises to tear down the law if he is elected," say Jonathan Allen and Jennifer Haberkorn at Politico. The GOP candidate argues that a Romney presidency is now the only avenue conservatives have left if they want to repeal ObamaCare, saying, "If we want to get rid of ObamaCare, we have to get rid of President Obama." Republicans have also seized on the key portion of Roberts' ruling that defined the individual mandate — which requires most Americans to buy insurance or pay a fine — as a tax. The GOP now claims that ObamaCare represents one of the most onerous tax hikes in recent memory, a talking point that could fire up conservative voters come November.

4. …But health care may still be a losing issue for Romney
Running to repeal ObamaCare may excite conservatives, but "many of the provisions of the law are popular," even if the individual mandate and law as a whole are not, says Balz. A debate on health care also "puts new pressure on Mr. Romney to explain how he would reform health care if he is able to overturn the law," a topic he has hardly discussed, says Michael D. Shear at The New York Times. And the stickiest problem for Romney is a familiar one, say Glenn Thrust and Maggie Haberman at Politico:  Explaining how his health care plan for Massachusetts, which also has an individual mandate, is any different from Obama's.

Read more political coverage at The Week's 2012 Election Center.