(CNN) Previously unreported details about President Donald Trump's unannounced visit to Walter Reed hospital in November 2019 have raised new questions about the precedent for a president to hand over power if they have to undergo surgery.
A forthcoming book from New York Times journalist Michael Schmidt reported that Vice President Mike Pence was on standby to temporarily assume the powers of the presidency in the case that Trump needed a surgical procedure requiring anesthesia. The White House declined to comment on the record to CNN about the report.
A temporary transition of power from the commander in chief to their vice president is laid out in section three of the 25th Amendment, a constitutional change brought on by the assassination of John F. Kennedy.
Dr. William Lang, a former White House physician who served under Presidents George W. Bush and Bill Clinton, told CNN's John King on Tuesday that if reports are true that Pence was put on standby in case Trump became incapacitated, then it may simply be a case of ensuring "all contingencies are covered."
But the Trump administration's reported decision not to make such contingencies public is a departure from two previous Republican administrations.
President Ronald Reagan was set to go under anesthesia for intestinal surgery at Bethesda Naval Hospital. He would be unconscious for a few hours as doctors removed a precancerous polyp.
Reagan administration officials knew they had to take a different approach to avoid criticism they faced in 1981 for not transferring power to the vice president when Reagan underwent surgery after he was shot in an assassination attempt, according to the New York Times.
So the morning of his surgery on July 13, 1985, Reagan signed a brief letter sent to the Senate president pro tempore and the House speaker transferring presidential power to then-Vice President George H. W. Bush.
"I am about to undergo surgery during which time I will be briefly and temporarily incapable of discharging the Constitutional powers and duties of the Office of the President of the United States," Reagan wrote.
From 11:28 a.m. until 7:29 p.m. on July 13, Bush was temporarily the "acting president" — the first in US history.
Recovering from the surgery and on painkillers, Reagan resumed the presidency in signing another letter, the Washington Post reported.
But there were questions over whether Reagan was indeed the first US president to formally invoke the third clause of the 25th Amendment. Media reports said that White House officials insisted Reagan's actions did not amount to a formal invocation of the amendment, but met its requirements.
The Republican president wrote that he was "mindful of the provisions of Section 3" and "the uncertainties of its application to such brief and temporary periods of incapacity."
"I do not believe that the drafters of this Amendment intended its application to situations such as the instant one," Reagan wrote. "Nevertheless, consistent with my long-standing arrangement with Vice President George Bush, and not intending to set a precedent binding anyone privileged to hold this Office in the future, I have determined and it is my intention and direction that Vice President George Bush shall discharge those powers and duties in my stead commencing with the administration of anesthesia to me in this instance."
And while Reagan and his administration reportedly took these steps to avoid setting precedent, the Times cited legal experts in writing that Reagan's actions did exactly that.
In 2002, Vice President Dick Cheney briefly assumed the powers of the presidency while President George W. Bush was sedated during a colonoscopy.
This time there was no question of whether section three of the 25th Amendment was invoked. Bush made the announcement himself as he left the White House for Camp David where he was scheduled to have the procedure done.
Explaining his decision to reporters to make Cheney the "acting president" for a few hours, Bush said, ''I did so because we're at war and I just want to be super -- you know, super cautious."
On June 29, 2002, he signed letters to congressional leaders, advising them of his transfer of power to Cheney and resumption of the presidency.
Bush did so again in 2007 for another routine colonoscopy, leaving Cheney temporarily in charge.
The University of Virginia's Miller Center in 1988 formed a commission to examine the 25th Amendment, which included the amendment's principal authors as co-chairs and former Supreme Court Chief Justice Warren Burger as one of 10 commissioners.
In its report, the commission wrote that any US president receiving anesthesia should use Section 3 of the 25 Amendment.
"The Commission believes that this mechanism should be made part of a routine course of action so that its invocation carries no implications of instability or crisis. Each president will have to make the decision and circumstances will be different. However, the Commission believes that use rather than non-use will create the sense of routine," the report read.
The commission also argued that it would "be wise" for a president to publicly state the transfer of power "so that the nation and the world are reassured, and to settle White House officials' fears of losing power."
"In short, let the president wave from his window to show he is up and around but convalescing while the vice president, as acting president under Section 3, takes care of the day-today business," the report said.