There's more on the line on Thursday at the Supreme Court than in any other court date former President Trump has had — for him, for the office of the presidency, and most of all, for the court itself.

Why it matters: The court's ultimate decision has the power to make or break Trump, and the court as an institution.

Driving the news: The court is set to hear oral arguments beginning at 10am over Trump's claim that he is immune from prosecution for his role in Jan. 6 — and that every president is immune from prosecution for any actions they took while in office.

• It's one of the most sweeping theories of presidential power ever articulated.
• In an earlier phase of the case, Trump's lawyers argued that a president couldn't be prosecuted even if they had a political rival assassinated.

The stakes for Trump are enormous, and yet the stakes for the high court are even higher.

• Even beyond the legal questions involved, "the court is almost on trial itself," Supreme Court scholar Grier Stephenson told the Wall Street Journal.
• A ruling shielding Trump from prosecution, handed down by a court on which he appointed one-third of the justices, could decimate what's left of the court's image as an institution that's above politics.

The big picture: There simply isn't very much precedent about how presidents interact with the civil and criminal justice systems.

• Most of it stems from a small handful of cases involving former Presidents Nixon and Clinton, and none of it has answered a question as sweeping as this one.
• Whatever the court decides here will shape the presidency forever.

Between the lines: Trump's lawyers have pursued the same initial strategy in all of his myriad court proceedings — try to delay things as much as possible, ideally until after the election.

• They have largely succeeded, including, to some extent, in this case. The justices rejected special counsel Jack Smith's request to expedite the proceedings.
• Even if they ultimately rule that Smith's case can proceed, it likely will not be finished by Inauguration Day.
• Trump has already won some significant victories at the high court. It unanimously rejected blue states' efforts to keep him off the ballot, and seems poised to scale back charges against other Jan. 6 defendants in a way that would also benefit Trump.

What we're watching: The court's ruling in this case will likely be the No. 1 blockbuster in a term that is full of blockbusters.

• The justices will be handing down rulings this summer on abortion, gun rights and the federal government's regulator power.
• But even those cases cannot match either the near-term, election-year consequences or the historic, democracy-defining implications of this one.