Final answer:
This behavior is referred to as grandiosity.
Step-by-step explanation:
This behavior is referred to as grandiosity in the context of mental health. Grandiosity is a symptom commonly seen in individuals with manic episodes, where they have an inflated sense of self-importance and believe they have exceptional abilities or powers. In this case, the patient's belief that they are on a secret mission given by the President and that they are the best fits the criteria of grandiosity.