Updated at 8:39 p.m. ET
Another surreal twist in the midst of another frenetic week has brought an unexpected question to the top of the conversation in Washington, D.C.
What is the 25th Amendment?
The short answer: It's a way, other than impeachment, provided by the Constitution for power to be taken away from a sitting president.
The long answer: The law provided an answer to painful questions posed by the assassination of President John F. Kennedy in 1963. The Constitution is clear that if a president dies or is killed, the vice president takes over.
But what happens if a president is grievously wounded? What if he or she is mentally incapacitated and can't continue doing the job responsibly?
"There was no legal way for the duties of the office to be discharged by anybody else, so the government would be paralyzed," as writer Evan Osnos told NPR's Terry Gross in an interview last year.
So the nation adopted the 25th Amendment, which was introduced in 1965 and ultimately ratified two years later. The text of the amendment is available here from the National Archives.
What the amendment spells out is a procedure by which members of the Cabinet can agree to notify Congress that they do not believe a president can carry out his or her duties. The officials could send a letter to Congress explaining why and, if Congress agrees by a two-thirds vote of both chambers, lawmakers could make the vice president "Acting President," under Section 4 of the 25th Amendment.
Does that mean the president would be taken out of office?
No. And, in fact, the original president actually could try to challenge this investiture of power in the vice president.
"[It's a] ... sort of nightmare scenario that scholars describe as contested removal, in which a president would object to the idea that he's been determined to be unwell," as Osnos said.
"And at that point, then Congress has three weeks to decide the issue. And you can just sort of imagine. It's kind of amazing to step back and think about what that would actually be like in practice, that you would have Congress actively, openly, publicly discussing the question of whether or not the president of the United States was mentally fit to return to the presidency."
This provision in law set up this situation for a reason: Suppose a president was badly hurt in an accident and was incapacitated for several months. The 25th Amendment ensures the vice president could lawfully carry out the duties of the office for that time. Then if the president recovered, he or she could take back over and serve the rest of the term without having had to resign.
The requirement for two-thirds majorities in Congress is designed to keep this process from being used for simple political reasons and ensure that Congress and the executive branch use the 25th Amendment only in situations — like the hypothetical accident — in which it is obvious to all this is necessary.
At the same time, as evidenced by Osnos' allusion to the "contested removal" scenario, it's possible that a president might not agree that all this was appropriate.
Are there any other checks and balances in this process?
Yes. The law says that an incapacitated president can resume the duties of the office "unless the vice president and a majority of either the principal officers of the executive department or of such other body as Congress may by law provide, transmit within four days to [legislative leaders] their written declaration that the president is unable to discharge the powers and duties of his office."
That's an important detail: If a 25th Amendment process were triggered, Congress could appoint a "body," or a board of medical experts, or other people, to give an opinion about the fitness of the president.
That might add legitimacy to all this in the midst of a crisis: The leaders of the Cabinet and the Congress could officially cite the diagnosis of a psychiatrist or other specialists.
Democrats who oppose Trump have introduced legislation that would create such a panel at least twice since Trump has been in office, Osnos told Gross — although because Republicans are the majority in the House and the Senate, the bills haven't gone anywhere.
Trump scoffs at all the discussion about his supposed mental health problems; he and supporters denounce what they call "Trump Derangement Syndrome" among opponents who are so alarmed they become unhinged by what he freely acknowledges is an unconventional presidency.
So the 25th Amendment is different from impeachment?
Yes. Impeachment — in which the House would introduce articles against the president and act as a grand jury, voting whether or not he would then stand trial in the Senate — removes a president altogether if convicted.
Congress could elect to use it in addition to the 25th Amendment in a crisis: Once a president had been sidelined and his or her power given to the vice president, Congress could then impeach the old president.
Washington would long have sailed off the map by that point. Although two modern presidents have faced articles of impeachment in the House, none has ever been convicted and removed from office, just as none has ever faced a 25th Amendment process.
Well, why is everyone talking about the 25th Amendment all of a sudden?
According to an op-ed in The New York Times on Wednesday, officials within the Trump administration have been talking about this amendment themselves.
The column writer, who has been described as "a senior official in the Trump administration," writes that people in the administration have been so unnerved about what they call Trump's erratic conduct that they've talked about using the 25th Amendment to take away his power.
"Given the instability many witnessed, there were early whispers within the cabinet of invoking the 25th Amendment, which would start a complex process for removing the president," the author wrote. "But no one wanted to precipitate a constitutional crisis. So we will do what we can to steer the administration in the right direction until — one way or another — it's over."
Trump said on Wednesday this is preposterous — the nation is thriving, he's the most successful president in decades, and that the op-ed is "gutless" for addressing the writer's grievances anonymously.
In a separate statement, White House press secretary Sarah Sanders said "the individual behind this piece has chosen to deceive, rather than support, the duly elected President of the United States."
"This coward should do the right thing and resign," Sanders added.