A full history should have been taken and a standardized battery of tests given, such as the Minnesota Multiphasic Personality Inventory. Among the other, more appropriate tests that should also have been considered are the Wisconsin Card Sorting Test, the California Verbal Learning Test and the Stroop Test. The MoCA examination was simply not sufficient under the circumstances to support Dr. Jackson’s declaration that he had “absolutely no concerns” about the president’s cognitive ability or neurological functions.

All of this matters because, if Dr. Jackson cannot be trusted to act independently when it comes to the president’s mental and physical health, we cannot be confident that he will do so when it comes to the fitness of the Department of Veterans Affairs. The department has the sacred charge of repaying our soldiers for their service by providing them with health care and other support. If Dr. Jackson tells the president — and the country — what Mr. Trump wants to hear about his own health, how can we trust him to honestly and rigorously diagnose the ailments of the V.A., and to treat them appropriately?

Having a candid V.A. secretary is all the more important because the department faces profound challenges. Since 2014, it has dealt with a pattern of negligent treatment at hospitals operated by one of its agencies, the Veterans Health Administration. Outgoing Secretary David Shulkin revealed yesterday that he had fought Trump administration proposals to privatize services provided by the V.A. — a move that could undermine the quality of health care provided to our veterans. Dr. Jackson’s treatment of the president does not inspire confidence that he will take on the V.A.’s problems with the brutal honesty that the job demands.

Dr. Jackson’s nomination is also undermined by the fact that although he is a medical professional, he lacks the management experience that the job demands. The V.A. secretary is responsible for a department that provides health care services to over nine million individuals. While Dr. Jackson has served his country with distinction, both in Iraq and as the White House physician, managing a relatively small medical team is not preparation for leading a vast and sprawling bureaucracy. The V.A. is one of the most complex health care management jobs in the world, and ideally would be run by someone with experience operating hospital systems or health businesses or enterprises, and large ones.

The nomination fits a pattern of cronyism, with the president appointing those of dubious qualifications to patronage jobs across the administration. The president’s former golf caddy is now the White House social media director. A contractor married to one of the Trump’s former household staff members now has a job at the Environmental Protection Agency. And a longtime friend of the Trump family who has been involved in planning golf tournaments and Eric Trump’s wedding is the head of the New York and New Jersey office of the Department of Housing and Urban Development. And now he has appointed his White House doctor to oversee the health care of millions of veterans.

Finally, in addition to concerns about independence and qualifications, it appears that Dr. Jackson had not undergone the normal vetting process for White House presidential personnel. Reportedly, the tweet-from-the-hip nomination of Dr. Jackson by the president surprised even his own advisers. That suggests that Dr. Jackson has not in fact received the careful review that is normally completed before such an announcement.

One of us worked (just down the hall from Dr. Jackson, actually) on vetting hundreds of senior administration officials. Very presentable and capable individuals — sometimes even those with existing security clearances — are sometimes disqualified by the rigorous personnel investigations that are normally undertaken for cabinet positions. Such cabinet-level vets complement but are more thorough than a typical pre-existing security clearance, and can uncover conflicts, misdeeds or other disqualifying information.

We are not suggesting that vetting will uncover anything improper, but caution is warranted, since many of Mr. Trump’s nominees have had unprecedented conflicts and other issues.