Chief Justice John G. Roberts Jr. has saved Obamacare for a second time, writing the majority opinion Thursday that upheld the health care law’s key provision of paying tax subsidies to customers in all states and saying the law otherwise would be a mess — something he doubted Congress intended.

The ruling holds that the Affordable Care Act authorized federal tax credits for eligible Americans living not only in states with their own exchanges but also in the 34 states with federal marketplaces.

Prevented major political showdown and millions from losing health care coverage. Decision was the second major court victory for the Obama administration on the president's signature health care law.

The immediate effect is that more than 6 million Americans, living in 34 states that haven’t set up their own exchanges but instead rely on the federal HealthCare.gov portal, will continue receiving subsidies, making insurance more affordable and preserving the economics underpinning the law.

The ruling was a complete victory for Obama, who said it puts a capstone on his legacy and should be the end of Republican efforts to overturn the 2010 law, known officially as the Patient Protection and Affordable Care Act.

Combined with a 2012 ruling, also authored by Chief Justice Roberts, Thursday’s decision settles the biggest legal questions surrounding the health care law and heads off the flashpoint that congressional Republicans hoped to use to force Mr. Obama to accept changes. If the justices ruled against the subsidies, millions of Americans would be left without the ability to pay for Obamacare coverage, which Republican leaders said would be their chance to negotiate changes.

The battle's not over -- a host of legal and political challenges remain, and if anything, Republicans say they are more emboldened than ever to repeal the law.

House Speaker John Boehner said in a statement on Thursday: "ObamaCare is fundamentally broken, increasing health care costs for millions of Americans. Today's ruling doesn't change that fact.”

Boehner vows to continue efforts on Capitol Hill to "repeal the law and replace it with patient-centered solutions."

Several court cases are still making their way through the system, including a challenge by House Republicans over the estimated $175 billion the administration is paying health insurance companies to reimburse them for covering poor people and cases over whether the law is forcing religious organizations to pay for employee contraceptives.

Republicans are weighing a repeal strategy that could lead to a veto showdown with the president before the end of the year. That's not to mention what might happen if a Republican wins the White House in 2016, with a GOP majority on the Hill.

Obama pressed Thursday for Washington to move on, but the law's harshest critics made clear they have no plans to do so.

The biggest fight may come on Capitol Hill, as Republican opponents consider using a filibuster-proof process called "budget reconciliation" to push a measure through the Senate and, with the help of the GOP majority in the House, get a repeal bill before the president.

Using this tactic is not unprecedented. When Democrats did not have the typically required 60 votes to pass ObamaCare in 2009, they used "reconciliation," which only requires a 51-vote majority, to pass parts of it through the Senate. The option of using the same process to get rid of the law, with only a simple majority, has been a topic of conversation among opponents ever