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."

Justice Samuel Alito addressed the "layers of protection" against bad faith prosecutions raised by the DOJ.

"I'm going to start with what the D.C. Circuit said. So, the first layer of protection is that attorneys general and other justice department attorneys can be trusted to act in a professional and ethical manner, right?" Alito said. "How robust is that protection?"

Alito continued that the "vast majority" of attorneys general and justice department attorneys "take their professional ethical responsibilities seriously" but that there have been exceptions.

In response, DOJ attorney Michael Dreeben agreed that there have been "rare exceptions" and said that "we're talking about layers of protection."

"I do think this is the starting point, and if the court has concerns about the robustness of it, I would suggest looking at the charges in this case," he said.

"The allegations about the misuse of the Department of Justice to perpetuate election fraud show exactly how the Department of Justice functions in the way that it is supposed to," Dreeben said. "Petitioner is alleged to have tried to get the Department of Justice to send fraudulent letters to the states to get them to reverse electoral results."