It must first be determined if “Christian” has an objective definition or can be applied to anyone who merely calls themselves one. I hear from anti-Christians all the time that the latter is enough, that if a person says they are a Christian, then they are. If such and such an act is done “in the name of Christ” or Christianity, then Christ or Christianity is responsible for it. This is patently absurd and a standard not applied to any other religion in the world. Even Islam escapes this tortured reasoning by many of the same people. “I slaughter these people in the name of Allah!” is excused as “not real Islam” and the perpetrators as “not true Muslims”!
Without going into all the New Testament passages which, collectively read, objectively define the true Christian, I think the answer can be found in the text and is quite simple: A Christian is a person who follows Christ. I will leave it to the reader to search the text for specifics, but here is a good place to start: What Does the Bible Say About You Are My Disciples If You Do What I Tell You To Do?
So, we then have to ask, “Does Donald Trump follow the teachings of Jesus Christ?”
You tell me.