The King Eternal, immortal and invisible, that the Apostle Paul writes about in this verse is the Lord Jesus Christ! He was not voted in and cannot be voted out. He is God!
His Kingdom is an everlasting Kingdom, and He rules it with righteousness and justice. Those who accept Him as King, Lord, and Savior now are warmly welcomed into His eternal family now and forever.
On the other hand, those who reject Jesus Christ now will be rejected by Him later. They will kneel at His Great White throne judgment in fear and trembling to receive God's eternal judgment on them. A judgment they choose by rejecting God's loving plan of redemption through Jesus Christ.
The good news is that those who call on the Lord Jesus Christ in humility, honesty, and with a repentant heart are instantly welcome in His holy presence. Our King Eternal sits at the right hand of God the Father, dispensing blessing and applying righteous judgment in the lives of all those He created! So call on the King Eternal, the Lord Jesus Christ, and entrust your life to His loving ways!