Trump, the Republican candidate challenging Democratic President Joe Biden in the Nov. 5 election, is the first former U.S. president to be criminally prosecuted.

The U.S. Supreme Court on Thursday confronts a major test of the power of the presidency in arguments over Donald Trump's bid for immunity from prosecution for his efforts to overturn his 2020 election defeat.

The justices at 10 a.m. EDT (1400 GMT) will hear Trump's appeal after lower courts rejected his request to be shielded from four election-related criminal charges on the grounds that he was serving as president when he took the actions that led to the indictment obtained by Special Counsel Jack Smith.

Trump, the Republican candidate challenging Democratic President Joe Biden in the Nov. 5 election, is the first former U.S. president to be criminally prosecuted.

Trump has pleaded not guilty in this case and in three other criminal cases he faces, including an ongoing trial on New York state charges related to hush money paid to a porn star shortly before the 2016 U.S. election that put him in the White House. Trump will not be attending the Supreme Court arguments because he will be in a Manhattan courtroom in that case.

The Supreme Court's 6-3 conservative majority includes three justices who Trump appointed: Amy Coney Barrett, Brett Kavanaugh and Neil Gorsuch.

The court already this year has handed Trump one major victory as he runs to regain the presidency. On March 4, it overturned a judicial decision that had excluded him from Colorado's ballot under a constitutional provision involving insurrection for inciting and supporting the Jan. 6, 2021, attack on the U.S. Capitol by his supporters.

Not since its landmark Bush v. Gore decision, which handed the disputed 2000 U.S. election to Republican George W. Bush over Democrat Al Gore, has the court played such an integral role in a presidential race.

Trump took numerous steps to try to reverse his 2020 loss to Biden. His false claims of widespread voting fraud helped inspire the attack on the Capitol on the day Congress met to certify Biden's victory. Trump and his allies also devised a plan to use false electors from key states to thwart certification.

The August 2023 indictment described Trump as "determined to remain in power" despite his election loss. Trump was charged with conspiring to defraud the United States, corruptly obstructing an official proceeding and conspiring to do so, and conspiring against the right of Americans to vote.