An important thing to know in trying to understand Borderline Personality Disorder (BPD) is the distinction between sufferers who are high-functioning and low-functioning.
About 6% of the population has this condition but only one in four end up receiving the diagnosis. The ones who are diagnosed are usually the low-functioning individuals who are suicidal, self-mutilate, abuse drugs, have eating disorders, and are severely depressed.
Many of the three-quarters who are never diagnosed fall into the high-functioning category. They may appear entirely normal to the outside world. They can be successful doctors, lawyers, engineers, CEOs of corporations, or leaders of countries. Though they may suffer the internal turmoils of this disease, they are often good actors and are able to suppress their impulses in public. The only ones who may observe their adverse actions are family, lovers, or close business associates. They may be driving these individuals crazy as they try to deal with the BPDs impulsive and irrational behavior.
Those with Borderline Personality Disorder are highly resistant to suggestions that they may have a problem and are loathe to seek psychological help. This explains why many of them are never diagnosed and why medical professionals have trouble recognizing them.
Mason and Kreger made a valuable contribution to psychology by pointing out the distinction between high- and low-functioning classes. They did this in their book, Stop Walking on Eggshells: Taking Your Life Back When Someone You Care About Has Borderline Personality Disorder. A good reference website about this mental illness run by one of the authors can be found at bpdcentral.com.
One reason those with BPD can be successful is that they see everything in black-and-white, all-good or all-bad terms. Since they view themselves as being all-good or all-bad, they can be driven by the need to feel all-good. This drive and perfectionist tendencies can lead to success in their studies and careers. The downside is they expect unobtainable perfection out of those around them. This results in their constantly finding faults in others resulting in chaotic relationships.
If Donald Trump has Borderline Personality Disorder he would clearly fall into the high-functioning group. He has been successful. As is typical of this class, he is driving those around him crazy. This includes those who come into close contact with him (government officials) but also the entire world.