The nine justices, three Trump appointed, will hear arguments on Thursday in his appeal of a lower court's decision to disqualify him from Colorado's Republican presidential primary under the US Constitution's 14th Amendment after finding that he participated in an insurrection.
Section 3 of the 14th Amendment bars from holding public office any "officer of the United States" who took an oath "to support the Constitution of the United States" and then "engaged in insurrection or rebellion against the same, or given aid or comfort to the enemies thereof."
Trump is not expected to be present at the arguments and will start his day at his Florida home and travel to Nevada, according to a source familiar with his plans.
Nevada on Thursday night holds a nominating caucus that Trump is expected to win handily as he cruises towards his party's nomination to challenge Democratic President Joe Biden on November 5.
The case calls on the Supreme Court to play a central role in a presidential contest unlike any since its landmark Bush v. Gore decision that handed Republican George W. Bush the presidency over Democrat Al Gore in 2000.
The justices also may soon confront another Trump-related case.
The former president faces a Monday deadline to ask the Supreme Court to intervene after a US appeals court rejected his claim for immunity in one of two cases in which he faces criminal charges related to his efforts to overturn his 2020 election loss to Biden.
The December 19 ruling by Colorado's top court came amid a wider - and mostly unsuccessful - drive by anti-Trump forces to disqualify him in more than two dozen other states over his actions relating to the January 6, 2021, Capitol attack.
Maine has also barred him from its ballot, a decision put on hold pending the Supreme Court's ruling in the Colorado case.
The justices could issue a decision quickly. Colorado's Republican primary is scheduled for March 5.
The Colorado case raises momentous questions for the Supreme Court, which has a six to three conservative majority.
Trump's lawyers have argued that he is not subject to the disqualification language because a president is not an "officer of the United States," that the provision cannot be enforced by courts absent congressional legislation, and that he did not engage in an insurrection.
In the January 6 incident, Trump supporters attacked police and swarmed the Capitol building in a bid to prevent congress from certifying Biden's victory.
Trump gave an incendiary speech to supporters beforehand, telling them to go to the Capitol and "fight like hell." He then for hours rebuffed requests that he urge the mob to stop.
The 14th Amendment was ratified in the aftermath of the American Civil War of 1861-1865 in which seceding Southern states that allowed the practice of slavery rebelled against the US government.
The plaintiffs who filed the lawsuit seeking to disqualify Trump - four Republican voters and two unaffiliated voters - have said a president clearly is an "officer of the United States" because "it would make no sense to read Section 3 as disqualifying all oath-breaking insurrectionists except the one holding the highest office in the land."
The justices could resolve the case without explicitly deciding whether Trump engaged in an insurrection.
The case also differs sharply from the criminal cases against him. The eventual ruling in the Colorado case, even if favourable to Trump, may not indicate how the justices would rule on his bid for immunity from prosecution as a former president.
