There are actually terms for Trump's behavior.  His need for adoration, being looked at, literally, as in the expression on people's faces, and talked about in glowingly parallel terms in speech or in writing.  It is called "narcissistic supply," and it is what narcissists live for above all else.  When they don't get it and they react vindictively, as Trump routinely does, it is called "narcissistic injury."   

His lack of a core center that contains an authentic self is what drives the continuous changes in his views, because he "mirrors" others, pretty much whoever he last spoke with that provided the necessary "narcissistic supply."    

Had the DSM not eliminated the diagnosis of narcissistic personality disorder from the cluster Bs, I'd bet a lot of money that Trump would be the poster child for NPD.  But the APA included NPD in the criteria for anti-social personality disorder recently, which identifies them "sociopaths."  

Pence must be a genius at manipulating him.