With nuclear codes in hands, why doesn’t the president get a thorough mental check?

With a tell-all book raising concerns about US President Trump’s mental stability, there is a renewed question asking why the most powerful man in the world is not required to pass a thorough mental health exam.

Trump defended himself as a “very stable genius” in a tweetstorm over the weekend. But his remarks have done little to quell questions swirling about why the man with the nation’s nuclear codes doesn’t have to undergo more rigorous mental health evaluations.

“I think it’s totally legitimate to ask about that and to have that as part of the examination,” said Julian Zelizer, a professor of history and public affairs at Princeton University and a CNN contributor. “I generally think that once someone’s president – or once someone’s even running for office – this should be fair game.

“This isn’t about scandal, and it’s not some kind of exposé. It’s understanding whether someone is fit to hold the office and whether there is any problem that the president himself – or his advisers, or the country – should be aware of.”

Trump, 71, is to undergo a medical exam on Friday by White House physician Dr. Ronny Jackson, who performed President Barack Obama’s last several physicals while he was in office. White House press secretary Sarah Huckabee Sanders has promised a readout of the results as soon as information becomes available, but it’s ultimately up to the president as to what information he wants to share with the public.

CNN reached out to multiple former White House physicians to learn what is routinely covered during the exams and what sort of mental health evaluations, if any, are done, but they were all unreachable or declined to comment.

The debate over a president’s mental acumen is not new. Former President Jimmy Carter sought to change the criteria in the mid-1990s, saying the president should be evaluated by an outside panel of medical experts because too much is at stake.

“At this time, the determination is made by the president’s personal physicians who must try to balance patient confidentiality and personal interest vis-à-vis the nation’s interest. We must find a better way,” Carter wrote in the December 1994 issue of the Journal of the American Medical Association.

Carter pushed for the formation of a nonpartisan group of medical experts, not involved in the president’s care, to be given the responsibility “for determining disability, thereby relieving the president’s physicians from their potential conflict of interest and enabling the 25th Amendment to work prudently and smoothly.”

The 25th Amendment allows for the vice president to assume the presidency if the sitting president is unable to do his job.

“The great weakness of the 25th Amendment is its provision for determining disability in the event that the president is unable or unwilling to certify to impairment or disability,” Carter wrote. “In this case, the constitutional duty to act falls on the vice president and a majority of the Cabinet. In such an unhappy event, it is absolutely necessary for the vice president and Cabinet to obtain accurate and unbiased medical advice to determine whether the president is able to perform his or her duties.”

Carter’s press secretary declined to make the former president available for this story. In October, he said the media were harsher on Trump than on most presidents.

Zelizer said it “shouldn’t really be a debate” as to a president’s mental fitness, because it’s imperative for the nation.

“The top concern of all is the power of the president to use and exercise force, whether it’s nuclear or whether it’s sending troops into a region of conflict. Either is bad – and that’s an area where you want to make sure that the president’s mind is working properly. So I think that should be the top issue,” Zelizer said. “More importantly, it’s important to the democracy: to know if the individual that holds that office is fit, mentally and physically.”

Dr. Gail Saltz, a clinical associate professor of psychiatry at NewYork-Presbyterian Hospital, said an internist should definitely ask questions of a senior about memory and mental status, because they’re on the front lines of early detection.

“If you’re a good internist, you do ask about those issues, because they should be caught and treated,” Saltz said. “It would surprise me if the White House is saying that there will be no psychiatric nor neurologic screening.”

The White House said Monday that Friday’s test will not include a psychiatric exam.

Dr. Nassir Ghaemi, a professor of psychiatry at Tufts Medical Center in Boston, explored the links between leadership and mental illness in his book “A First-Rate Madness.” He issues a cautionary tale on dismissing a leader over mental health issues, because some of the greatest figures in history, such as Winston Churchill and Abraham Lincoln, suffered from episodes of depression and benefited from it in times of crisis.

“People with mild manic symptoms are more creative and more resilient to stress than normal mentally healthy people,” Ghaemi said on CNN’s “Smerconish” on Saturday.

In his new bestseller “Fire and Fury,” author Michael Wolff says that aides close to President Trump have raised concerns about his mental health and that discussions about replacing him are “alive every day in the White House.” CNN has been unable to verify all of Wolff’s claims.

“It’s not unreasonable to say this is 25th Amendment kind of stuff,” Wolff said on NBC’s “Meet the Press.”

Citing people close to the president, Wolff has said the president has begun repeating three stories in conversations in less than 10 minutes, when he used to repeat stories in about a 30-minute window. Wolff told CNN’s Christiane Amanpour that “100% of the people around the president believes he’s incapable of carrying out the duties of office.”

In full damage control, Trump and the White House beat back over the weekend, trashing Wolff and his book as fiction and tabloid garbage while defending the president’s mental fitness.

“Actually, throughout my life, my two greatest assets have been mental stability and being, like, really smart,” Trump said in a tweetstorm that began Saturday.

Secretary of State Rex Tillerson told CNN late last week that he has “never questioned” the president’s mental fitness, and “I have no reason to question his mental fitness.” CIA Director Mike Pompeo reiterated that message on Sunday, saying the book’s assertions on the president’s mental abilities “are just absurd.”

“This president reads material that we provide to him. He listens closely to his daily briefing,” Pompeo said on “Fox News Sunday.”

Rep. Adam Schiff, a California Democrat, gave a different assessment. “Plainly, we have a seriously flawed human being in the Oval Office,” Schiff said Sunday on CNN’s “State of the Union.”

Trump is scheduled to have his physical Friday at Walter Reed National Military Medical Center in Maryland. Test results typically take several days before the findings are known, but what information is released and when is ultimately at Trump’s discretion.