Nominal, that is, one assumes.

Their '20 year rule' speaks mountains about what they think Trump's devotion is. The other presidents during that period were unequivocally Christian.

@DenisdeBernardy Not necessarily. As far as I can tell, it simply means they don't want to get into a debate over it and aren't going to make an exception for this specific case. reddit.com/r/AskHistorians/comments/45wqkl/…

I have my doubts that any of them an be considered Christians

Regardless of the answer to this question, you may be interested in xkcd.com/1122.

Is Carter the most recent genuinely Christian president?

At a time when the constitution of Vermont said only Protestants could hold public office, Ethan Allen, whose amateur book on theology makes his non-Christianity clear, was allowed to hold offices in that state. So people don't pay close attention in judging religious qualifications.

Has the United States ever had a True Scotsman president?

@axsvl77 : This would just lead to the "No true Scotsman" fallacy, so best be quite generic with the definition of "Christianity".

@axsvl77 Can you explain what you mean?

I'm sorry, but all of the given answers only serve to demonstrate how fundamentally opinoin-based this question is.

@user76284 It is a sarcastic/obnoxious/humorous comment about about the type of people that become presidents. Also a little sad. The idea is this: there are two ways to define a person as Christian. One way is sort of like asking if someone is a member of a club - do they attend church regularly, tithing, etc? This is a weak definition. The second, more rigorous definition, is probably better described do they behave in a Christian manner.

@user76284 A prime example of this is George W Bush.. He claimed to be a Christian - but he lied to millions about Iraqi WMD to precipitate a war that has claimed many lives, with the goal of enriching himself and others. In my view, it is difficult to call GW Bush, a person who starts a war for the purpose of material profit, a Christian. Perhaps if he stood trial as a war criminal, and apologized for his actions, he could become a Christian.

@axsvl77 Yep, that's falling for the "True Scotsman Fallacy" everybody's talking about here.

@axsvl77 Indeed. IIRC the majority of Christians wouldn't count as "real" because they don't hate enough - if you only take the viewpoint of the Westboro Baptist Church.

@R.Schmitz Yes, true. Also, don't get me started on the "Christian" soldiers who subjugated the earth during the colonial era.