At least when it comes to presidents:
Whereas you might think that narcissism would be part of the job description for anybody aspiring to become the chief executive of the United States, American presidents appear to have varied widely on this psychological construct. In a 2013 Psychological Science research article, behavioral scientists ranked U.S. presidents on characteristics of what the authors called “grandiose narcissism.” Lyndon Johnson scored the highest, followed closely by Teddy Roosevelt and Andrew Jackson. Franklin D. Roosevelt, John F. Kennedy, Nixon, and Clinton were next. Millard Fillmore ranked the lowest. Correlating these ranks with objective indices of presidential performance, the researchers found that narcissism in presidents is something of a double-edged sword. On the positive side, grandiose narcissism is associated with initiating legislation, public persuasiveness, agenda setting, and historians’ ratings of “greatness.” On the negative side, it is also associated with unethical behavior and congressional impeachment resolutions.
Which explains my mixed feelings towards a potential Trump presidency. The guy could do great things, but he could also blow up the world, or irretrievably damage the values that make America unique.