1 John 1:9. If you confess your sin he is faithful to cleanse us of sin and and unrighteousness,!!
I am concerned as to how Piper got this wrong. David seduced Bathsheba, killed her husband, and took Bathsheba as his third, I think, wife. Solomon had a legal relationship with 1000 women. (For those who say concubines are not wives, I answer that no, they are not. But concubines did have some legal rights of their rank.) Those men were no worse, morally, than Trump.
Lately, Trump has been saying and doing the "right" things as far as being a Christian is concerned. Since God did not give me, or John Piper, and "elector detector" I cannot speak to Trump's position before the Lord.
Which brings me down to what does give a person a right position before the Lord. ONLY RECOGNIZING THAT YOU ARE A SINNER AND THEREFORE SEPARATED FROM GOD; REALIZING THAT JESUS IS GOD'S ONLY PROVISION FOR YOUR SIN; AND ACCEPTING THE FORGIVENESS AND RECONCILIATION AVAILABLE IN THE PERSON AND WORK OF JESUS CHRIST.
That's it. That's all. There is no more to it. It's available to me, to you, to John Piper, and to Trump. It's available to ALL.