I would think such a personality disorder would make him very unpredictable and erratic. Yes, I know Trump considers that his secret weapon, the opposition can never figure out how he might respond. Now that may work in business negotiations where money talks, but in high stakes political negotiation where the lives of million of people and possibly the fate each nation hangs in the balance, each leader must be able to anticipate the reactions of the other as well as the reactions of political forces driving the other leader...
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You bring up a good point. If Tiny Hands suffers from NPD (actually it's always the people around them who suffer), he can't anticipate the reactions or feelings or drives or motivations, indeed any marker at all of another person that makes them separate or unique from him. That's one of the hallmarks of the disease. NPDers see the world and the people in it as all extensions of his own will or as potential admirers. It doesn't matter what admirers think when their only function as far as an NPDer is concerned is to bask in his greatness. So armed with a complete vacuum of being able to put himself in other people's shoes (since other people really don't exist in the mind of an NPD), it is impossible for them to anticipate any unique state of mind another person might possess. And even if they could, it's highly offensive to them that they would be asked to acknowledge another at all as mattering.
I forget where I read it but I found something funny that an NPD researcher said. He said that if you want to cause smoke to come out of an NPDer's ears, ask them a simple question. Ask them while you're discussing a topic, "how do you think I feel about that?". It sends them reeling because they CAN'T answer the question.
Another great psychological trick is to ask them to discard their perennial need to be admired. Once I asked a person with NPD who professed themselves sympathetic to the poor (needed to be admired in contrast to their miserable lives) to do an exercise. I said for them to walk up to a complete stranger, someone in a public spot that looked absolutely on the down and outs, who needed cash and was hurting. The task was for the narso to hand the stranger a $20, without looking into their eyes or having any facial expression at all (no recognition for the act on any level), and then turn briskly on her heels and walk away without looking back. The narso woman fought hard against the task. She went on and on about "why would I do such a thing without at least getting some type of acknowledgment?!" "That's "sick!" she exclaimed. On and on and on. I calmly retorted that it wasn't the end of the world and if she could succeed she could show me that she didn't have the need to be admired. She refused on the spot and not without a great addition of emotional spew, finally hurling insults at me, predictably, and demanding an audience we were having the conversation in front of do a version of verbally stoning me to death...lol..
The point being that they all seem to function with the same hard and fast symptoms. Remember when Tiny Hands had the gal come to the podium and then he offered her a job on the spot? It was theater. At once he would be admired for being generous and in contrast to her poor miserable little life, he would seem even grander. They all function the same. And you're right, the prospect of one running the country makes Obama look like a success story on par with Abraham Lincoln. I'm not joking when I say that the earth might become the 2nd asteroid belt in our solar system if Tiny Hands isn't properly admired or appears to be second fiddle in substance to another world leader. Remember, he's not taking nukes off the table!..