The Archbishop of Canterbury, Justin Welby, is puzzled. Like many Christians on this side of the Atlantic he doesn't understand why Christians in the US seem to have supported Donald Trump in such numbers. Or perhaps to put it another way – he doesn't understand why evangelicals seem to have overwhelmingly supported Donald Trump. I have militant atheist friends who delight in pointing me to President Trump's latest aberration before they gleefully point out he is 'my' President – ie the Christian President. But is he?

The hostile atheists and secularists take great delight in tweeting about a 'far right, misogynistic, racist, sexual hypocrite, Christian' (forgetting both his past as a New York, liberal Democrat and the sexual exploits of their hero JFK). He is the ideal candidate for them to use to justify their hatred for Christians.

On the other hand there are Christians who think that Donald Trump is 'our' candidate, the one chosen and anointed by God. The one who though he is flawed (the 'we are all sinners' card usually gets played at this point) is still far better than the alternative. He is the Christian President.

Except it's not as simple as that. There are professing Christians who are strongly opposed to Donald Trump. John Macarthur made clear his opposition to the 'vulgar Trump', as did Russell Moore of the Southern Baptists and many others.

Ah – but didn't 80 per cent of evangelicals vote for Trump? Didn't they do this partially because Trump appointed the clearly evangelical former Catholic Mike Pence as Vice President? Isn't he beholden to Christians, and don't most Christians support him?

So what can we say? What is the answer to the question?

1. Donald Trump is not a Christian – so he cannot be the 'Christian' president. I wonder why people consider Donald Trump to be a Christian when he shows no evidence of knowing Christ or of following him? He has given no evidence of having a real faith in Christ or shown any of the fruits (and as Christ said 'you shall know them by their fruits'). As a Christian that is not a big issue for me regarding his role as President, although as a human being I do pray for his salvation. I understand and rejoice in the fact that Mike Pence is a professing Christian with a real faith and understanding of the Scriptures. That doesn't necessarily make him a good politician, but I would hope he would be a Christian witness and moderating influence on the President. Those Christians who voted against Bill Clinton because of his moral character and yet voted for Trump despite his moral character were hardly being consistent.

2. The majority of evangelicals did not vote for President Trump. The 80 per cent figure includes only those who voted, only whites (forgetting that many African-Americans and Hispanics and Asians are evangelicals) and includes as evangelicals many people who don't even go to church. However it is the case that the majority of white evangelicals in this broad sense who did vote, probably did vote for Trump.

3. Many Christians from different backgrounds did vote for President Trump – but they will have done so for a variety of reasons. Some cultural, some personal, some political. Many did not like the alternative and they were not really given much choice. They were also concerned about issues like the Supreme Court Justices, abortion and the fact that Hilary Clinton would have almost certainly limited religious freedom. That however still does not make Donald Trump the Christian President. The fact that his policies were perceived to be less bad than the alternative is not exactly a ringing endorsement.

4. The 'Christianity' that supports Trump is often not Christian. I don't mean by this that real Christians don't vote for Trump – many did, and for the reasons said above. But many who profess to be Christian are either very loose in their Christianity or embrace heresies like the Prosperity Gospel. It may be that the Prosperity Gospel fits better with the gold of Trump towers than it does with the gospel of Jesus Christ.

5. God did not ordain Donald Trump as President, but he did ordain that Donald Trump should be President. Spot the difference. It's not as though God said about Trump, 'He's my man. I choose him.' But neither is it the case that the American electorate took God by surprise and now he's on to plan B. Often God ordains that we get the consequences of our own actions and wishes. Because God can overrule any evil for good, does not mean that he approves of, or endorses the evil (please note I am not saying that Donald Trump is evil – at least no more than any other human being! If we had been talking about President Clinton the same would have applied.) We don't know yet but it could be that God has ordained Trump for judgement – or mercy!

6. You cannot have a Christian President, but you can have a President who is a Christian. Christianity is not an ethnic, political or social force. We don't vote for people just because they share our faith any more than we choose a plumber because they share our faith. I know its a little more complex than that, because of course in politics there are more values issues, but even so it is the case that you could be a good Christian and a bad politician, and a bad Christian and a good politician (Winston Churchill springs to mind!). There are also many policies which Christians will have different views on – is there a Christian view on Brexit? Or on how much tax we should pay? Or on Canada? Our Christian values will influence all of these, but the Bible is not a political manual. That's why you can have Christians who are right-wing, left-wing and all the feathers in between.

There is much more that could be said but the above makes it clear – Donald Trump is not the Christian President. To those atheists and secularists who want to pin Trump on Christianity – please don't. It isn't true.

To those evangelicals who have signed up as Trump supporters and endorsers – please stop it! If you think Trump is the next David or Moses, or God forbid, Christ, then you are in for a big let down. Support him in terms of praying for him, respecting him, praising him when he does what is right and challenging him when he does what is wrong. But please don't tie Christianity in with Donald Trump. Our faith is in Christ, not in Trump, nor in any of our leaders.

And please let us not identify our politics with Christ lest Christ becomes identified with our politics. The American Church needs to grasp how much of an embarrassment it is to the rest of the Church in the world that it is identified (rightly or wrongly) with a President whose behaviour and speech is far removed from that of a Christian. That is not because of our politics (Christians have all sorts of different politics) but because of our love for Christ and his world. Maybe it's time for a refocus on what our real priorities are – or should be?

David Robertson is Associate Director of Solas CPC in Dundee and minister at St Peter's Free Church. Follow him on Twitter @TheWeeFlea.