During oral arguments in three cases Tuesday, the justices will explore Trump's claim that he cannot be subjected to subpoenas or any criminal investigative process, by virtue of the demands of the presidency.
The assertion of expansive presidential power comes as Trump faces an array of mounting requests for his personal and business financial records. His efforts to challenge the subpoenas in federal courts have, so far, been unsuccessful at every level.
"These are critical cases that are going to decide whether or not a president, in office, has presidential immunity for the duration of the time that he is sitting in office," said Claire Finkelstein, a criminal law expert at the University of Pennsylvania Law School and director of its Center for Ethics and the Rule of Law.
"It would literally put the president above the law if the Supreme Court sides with the president's lawyers in this case," Finkelstein said.
The outcome will also determine whether Trump -- the only modern American president to have not publicly released tax returns or divest from major business interests while in office -- has to share more personal financial information with voters before the November election.
Three Democratic-led House committees and Manhattan District Attorney Cyrus Vance are seeking multiple years of documents as part of their respective investigations into potential wrongdoing by Trump prior to his presidency. The subpoenas are addressed to Trump's personal accounting firm, Mazars USA, and three financial institutions used by him and his business. Trump intervened to block the third parties from complying.
"These subpoenas are all expansive, burdensome, and unfocused fishing expeditions. They are inappropriate and should be invalidated," Trump's personal attorneys argued in court briefs.
The Trump legal team further claimed the requests are politically-motivated, illegitimate and a distraction from the important duties of presidential office. The Justice Department has filed an amicus brief siding with the president.
"The president cannot effectively discharge those duties if any and every prosecutor in this country may target him with criminal process," the Trump lawyers added.
Vance, a Democrat, has said he's seeking the records for an ongoing criminal probe into possible violations of state financial laws by Trump and the Trump Organization. The lawmakers say the information they seek is critical to drafting of federal ethics and anti-corruption legislation involving presidents.
"The mere risk of interference with official functions does not afford a president categorical immunity against subpoenas for documents concerning private conduct," Vance wrote in his brief. "Presidents throughout history have been subject to judicial process in appropriate circumstances."
In 1974, the Supreme Court ruled unanimously that President Richard Nixon had to obey a subpoena from the Watergate special prosecutor and turn over tapes and documents, limiting "executive privilege" protections for certain presidential communications.
Twenty-three years later, the court rejected President Bill Clinton's claims of broad immunity from litigation while in office, requiring him to participate in a videotaped deposition in a civil case involving Paula Jones, a former Arkansas state employee who accused Clinton of sexual harassment.