AUDIE CORNISH, HOST:

Here's another quote from the author of that anonymous op-ed. Given the instability many witnessed, there were early whispers within the Cabinet of invoking the 25th Amendment. The claim has serious implications. The 25th Amendment provides a way to take power away from a sitting president, an alternative to impeachment, though it's never been used. Yale law professor Harold Koh co-authored an in-depth report on the 25th Amendment. As he explains, its origins date back to the assassination of President Kennedy.

HAROLD KOH: Well, in that period in the early '60s, a lot of questions arose about exactly how presidential succession ought to occur, particularly if the president is physically disabled by an assassination attempt or something else. And so members of Congress consulted experts and in 1967 came forth with this amendment.

There were two provisions that count. One is how the president could himself say he's unable for a particular period. For example, if he's going under anesthesia for a medical procedure, he can submit a letter. That's been done on a number of occasions. But Section 4, which has never been invoked, is, what if the president appears to be unable to discharge the powers and duties of the office and those close to him see it? And that created this procedure where the vice president and eight principal officers can remove him for four days. And if he disputes it, it goes to both houses of Congress to be resolved within 21 more days.

CORNISH: And to be clear, this isn't about just medical issues, right? I mean, what is the standard for a president not being able to meet his duties?

KOH: Well, the standard is inability. And inability can amount in all kinds of circumstances. If the president were kidnapped, he would be perfectly healthy, but he wouldn't be able to discharge the powers and duties of his office. So the vice president could declare inability, but then if he's released, you can declare ability again. That's happened on various television shows and things like that that dramatize this.

A more complicated situation is if the president is behaving erratically or becomes very ill. And those kinds of things require an assessment of inability. But the key thing is that the word inability is not a medical term. Obviously medical factors may be relevant to determining whether someone's able to discharge the powers and duties of the president. But in the end, it's a political determination to be made by those who are observing him conducting the office.

CORNISH: As we've said, this is never been done. And when you read this op-ed and this was raised at all, did it surprise you?

KOH: Well, the people who are in the best position are those who are close to the president, the people who are seeing him or her every single day. So what we saw was an insider's account that they thought that this was a possibility.

Just to give an example, toward the end of the Reagan administration, which we now know the president had early Alzheimer's, you know, Howard Baker became chief of staff. And he thought that maybe the 25th Amendment ought to be invoked. So the journalistic account is that people were brought in to observe him, but on that particular day, Reagan was in very good health, and so they decided that they wouldn't go forward. And it was very close to the end of an eight-year presidency anyway. That was the only time or the - probably the last time it was very seriously considered.

CORNISH: If the 25th amendment were to be invoked, everything would happen very quickly. Do you worry that that would just be chaos?

KOH: Well, the purpose of our writing this report was to try to give some clarity. We were worried that people would give different provisions or words, a self-serving interpretation at that particular moment and that very few people would go back and actually read what went into the framing of this amendment. So we read all of the legislative history. We consulted all of the experts on the 25th Amendment. And we wanted to give just an interpretation of both the process and what the words mean under that circumstance. You know, this should not be decided by talking heads going on cable news. It should be done according to the Constitution.

CORNISH: Harold Koh is a professor at Yale Law School and co-author of a "Reader's Guide To The 25th Amendment." Thank you for speaking with us.

KOH: Thank you.

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