STORY: The U.S. Supreme Court's conservative justices on Thursday signaled sympathy to the argument that presidents have some immunity against criminal charges...

...as Donald Trump seeks to be shielded from Special Counsel Jack Smith's federal election subversion case.

During oral arguments, conservative Justice Samuel Alito expressed concern about presidents having to worry about being indicted after leaving office.

"...will that not lead us into a cycle that destabilizes the functioning of our country as a democracy?"

Liberal Justice Elena Kagan probed hypothetical examples of presidential wrongdoing.

"If a president sells nuclear secrets to a foreign adversary, was that immune?"

Conservative Justice Neil Gorsuch, a Trump appointee, stressed the historical importance of the decision before the court, which has a 6-3 conservative majority.

GORSUCH: "The dangerousness of accusing your political opponent of having bad motives, and if that's enough to overcome your core powers or any other limits. Reactions? Thoughts?"

TRUMP ATTORNEY D. JOHN SAUER: "You're raising a very difficult question."

GORSUCH: "That's the idea... You also appreciate that we're writing a rule for the ages."

Trump, the Republican candidate challenging Democratic President Joe Biden in the Nov. 5 election, has pleaded not guilty in the federal election case.

He has claimed he is immune from prosecution for trying to undo his 2020 election loss... on the grounds that he was serving as president when he took the actions that led to his indictment.

Trump spoke about his immunity claim before heading into a New York court for another of his four criminal cases... this one over hush money paid to a porn star.

"The President has to have immunity. This has nothing to do with me. This has to do with a precedent in the future for 100 years from now, if you don't have immunity, you're not going to do anything. You're going to become a ceremonial president."

The justices would need to rule by about June 1 for Trump's trial to be held before the election, according to legal experts.

A ruling is expected no later than the end of June.