The Supreme Court said Monday it will take up a closely-watched challenge to the Affordable Care Act as Democrats work to save the health care law.

The justices likely won't hear the case until its next term, which begins in October, with a decision coming by the end of June 2021.

The case hardly marks the first time the Supreme Court will hear a dispute involving Obamacare. Most notably, in 2012, the high court upheld the health care law's individual mandate, which is considered to be the heart of Obamacare and requires all Americans to purchase health insurance coverage, in a 5-4 vote.

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The five justices who upheld the individual mandate — Chief Justice Roberts and Justices Ruth Bader Ginsburg, Stephen Breyer, Sonia Sotomayor and Elena Kagan — all remain on the court.

But President Trump and the GOP-controlled Congress have already taken steps to dismantle the health care law, which was enacted in 2010.

As part of Republicans' overhaul of the tax code in 2017, Congress abolished the financial penalty for individuals who do not purchase health insurance. The move prompted a group of GOP-led states to file a lawsuit challenging Obamacare, arguing the individual mandate is unconstitutional because the fine had effectively been eliminated. The red states — with the Trump administration in agreement — also said that because the mandate could not be separated from the rest of the health care law, it should fall.

In 2018, a federal district court judge in Texas agreed with the states that the individual mandate is unconstitutional and struck down the entire Affordable Care Act on grounds that it cannot survive without the mandate. The judge put his ruling on hold while litigation continued.

Then, in December, a divided panel of judges on the 5th U.S. Circuit Court of Appeals also ruled that the individual mandate is unconstitutional. But the New Orleans-based court did not decide the question of whether the rest of Obamacare could stand without the mandate and sent the case back to the lower court to reconsider the issue.

Twenty states and the District of Columbia and the Democratic led-House of Representatives, all of which intervened in the case, asked the Supreme Court in January to fast-track review of the legal battle over Obamacare and decide the case before the end of its current term. The questions raised by the case, they argued, cannot be left unanswered for a prolonged period of time.

The 5th Circuit's decision "poses a severe, immediate and ongoing threat to the orderly operation of healthcare markets throughout the country, casts doubt over whether millions of individuals will continue to be able to afford vitally important care, and leaves a critical sector of the nation's economy in unacceptable limbo," lawyers for the House wrote in their request to the Supreme Court.

But the Republican states and the Trump administration opposed the efforts to expedite review of the 5th Circuit's ruling, writing to the court that the decision "creates no present, real-world emergency."

"The appropriate course is instead to defer any review in this court until after the district court has completed its reassessment of severability on remand and the court of appeals has reviewed that determination on appeal," Solicitor General Noel Francisco said. "That approach not only will ensure that the court has the benefit of the lower courts' considered views, but it also may narrow the scope of the issue ultimately presented to this court."

The Supreme Court rejected the fast-track request last month, reducing the chances that the justices will decide the case before the 2020 presidential election.