Minutes into arguments, Justice Sonia Sotomayor raised the question of whether immunity extends to political assassinations.

The issue was discussed at length in a lower court hearing. Then, Trump attorney John Sauer suggested Trump could be immune, under certain circumstances.

"I'm going to give you a chance to say if you stay by it," Sotomayor said. "If the president decides that his rival is a corrupt person and he orders the military, or orders someone to assassinate him, is that within his official acts for which he can get immunity?"

"It would depend on the hypothetical, but we could see that could well be an official act," Sauer said.

Justice Ketanji Brown Jackson pressed Trump attorney John Sauer on his contention that without immunity all future presidents would feel paralyzed to take official acts while in office that could put them in criminal jeopardy.

"I mean, I understood that every president from the beginning of time essentially has understood that there was a threat of prosecution [upon leaving office]," Jackson said.

Sauer responded by quoting Benjamin Franklin from the constitutional convention, to which Jackson seemed skeptical.

"But since Benjamin Franklin everybody has presidents who have held the office [who knew] that they were taking this office subject to potential criminal prosecution, no?" she said.

Justice Clarence Thomas opened questioning by getting to the heart of the case: where is the "source" of presidential immunity and how would the court come to decide what acts fall under that scope.

First, he asked Trump's attorney to be "more precise as to the source" of supposed presidential immunity.

John Sauer responded that it comes from the executive vesting clause of the Constitution.

Thomas then pressed how exactly the court would "determine what an official act is," to which Sauer said acts fall within the “outer perimeter” of a president's official duties.

Trump's attorney, John Sauer, addressed the justices first, saying in his opening statement that unless presidents are granted the absolute immunity that Trump seeks, "Every current president will face de facto blackmail and extortion by his political rivals while he is still in office."

Sauer also called out controversial policies of other commanders in chief, such as George W. Bush's regarding the Iraq War and a Barack Obama-approved drone strike against a U.S. citizen as part of anti-terrorism operations overseas, while saying the implications of the court's decision here "extend far beyond the facts of this case."

As the questioning of Trump's attorney continues, Justice Elena Kagan noted that the framers of the Constitution consciously did not put in an explicit presidential immunity clause.

"They didn't provide immunity to the president," she told lawyer John Sauer. "And you know, not so surprising, they were reacting to a monarch who claimed to be against the law. Wasn't the whole point that the president was not a monarch and the president was not supposed to be above the law?"

In response, Sauer argued that the framers did put in an immunity clause "in a sense" with the executive vesting clause and that they adopted impeachment as a "structural check," which is a major part of Trump's defense against his federal charges.

"They did discuss and consider what would be the checks on the presidency and they did not say we would have criminal prosecution," Sauer said. "Everybody cried out against that as unconstitutional."