Also, please remember that Paul the Apostle called himself the chief of sinners before he became an apostle of Jesus after the Lord appeared to him on the road to Damascus. He was relentless in his persecution of Christians and even voted to put Christians to death. He was there when Stephen was stoned and consented to his death. He helped drag Christian men and women to prison.
All this and yet God chose him. When he met Christ he forgot the things of his past, all his sins and failures, and pressed on to do what God called him to do. He ended up writing at least 13 books of the New Testament which came through a revelation of Jesus Christ. Galatians 1:12
If God can choose men like King David and Paul who obviously committed some horrible sins including murder, God can choose Donald Trump.
Just a side note, this should bring encouragement to all of us. None of us are too great a sinner for God to work with. He has chosen all of us for something. There is hope for all of us if we are willing to accept God's ways in our lives.