People always say that this is a Protestant doctrine, but really it goes back to Jesus and was well expounded first by Augustine. Basically, the church and earthly government are different. The business of the church is to preach the Gospel, forgive sins, deliver mercy. The business of the government, and of heads of state, is to be the means through which God provides temporal order. So the job of the president includes, importantly, keeping citizens safe. Christians can disagree about all manner of how to enact any policy, when Scripture doesn’t mandate a particular one, but they should always be motivated by love of neighbor. And, as I discussed previously, there are all sorts of thoughts on how to rank concerns for neighbors. One’s obligation to your nearest neighbor of wife and infant daughter are more pressing than obligations to neighbors in other countries.

So if Donald J. Trump becomes president, his primary responsibility would be to those who are entrusted to his care, namely U.S. citizens. As a Christian, he should pray for everyone throughout the world and show love to them in his vocation as a Christian, but in his vocation as president, his duty would be to keep Americans safe.