For once we agree.
There is no way to diagnose trump as Narcissistic Personality Disorder, as the criteria is quite extensive, and you would need a thorough history of him.
This is the current criteria to diagnose Narcissistic Personality Disorder (according to the DSM-V):
The essential features of a personality disorder are impairments in personality (self and interpersonal) functioning and the presence of pathological personality traits. To diagnose narcissistic personality disorder, the following criteria must be met:
A. Significant impairments in personality functioning manifest by:
1. Impairments in self functioning (a or b):
a. Identity: Excessive reference to others for self-definition and self-esteem regulation; exaggerated self-appraisal may be inflated or deflated, or
vacillate between extremes; emotional regulation mirrors fluctuations in self-esteem.
b. Self-direction: Goal-setting is based on gaining approval from others; personal standards are unreasonably high in order to see oneself as
exceptional, or too low based on a sense of entitlement; often unaware of own motivations.
AND
2. Impairments in interpersonal functioning (a or b):
a. Empathy: Impaired ability to recognize or identify with the feelings and needs of others; excessively attuned to reactions of others, but only if
perceived as relevant to self; over- or underestimate of own effect on others.
b. Intimacy: Relationships largely superficial and exist to serve self-esteem regulation; mutuality constrained by little genuine interest in others‟
experiences and predominance of a need for personal gain
B. Pathological personality traits in the following domains:
1. Compulsivity, characterized by:
a. Rigid perfectionism: Rigid insistence on everything being flawless, perfect, without errors or faults, including one's own and others' performance;
sacrificing of timeliness to ensure correctness in every detail; believing that there is only one right way to do things; difficulty changing ideas and/or
viewpoint; preoccupation with details, organization, and order.
2. Negative Affectivity, characterized by:
a. Perseveration: Persistence at tasks long after the behavior has ceased to be functional or effective; continuance of the same behavior despite
repeated failures.
C. The impairments in personality functioning and the individual‟s personality trait expression are relatively stable across time and consistent across situations.
D. The impairments in personality functioning and the individual‟s personality trait expression are not better understood as normative for the individual‟s developmental stage or socio-cultural environment.
E. The impairments in personality functioning and the individual‟s personality trait expression are not solely due to the direct physiological effects of a substance (e.g., a drug of abuse, medication) or a general medical condition (e.g., severe head trauma).