How can a demonic spirit co-exist with the Spirit of Christ? It cannot.
How can a demonic spirit co-exist with the Holy Spirit which is in our soul? It cannot. The only way any demonic activity can exist is if we give it a mind outside of the mind of Christ. We must give the power to give any outside influence to anything that is not of Christ and The Holy Spirit.
We are being lied to if we believe that demonic possession can overpower the Spirit of Christ we are born again with.
Ro 8:2 For the law of the Spirit of life in Christ Jesus hath made me free from the law of sin and death.
Ro 8:9 But ye are not in the flesh, but in the Spirit, if so be that the Spirit of God dwell in you. Now if any man have not the Spirit of Christ, he is none of his.
Ro 8:10 And if Christ be in you, the body is dead because of sin; but the Spirit is life because of righteousness.
If we believe the lie, The Holy Spirit has been given a back seat to our soul/minds and what we believe is the deception of the demonic activity.
Romans 8:11 But if the Spirit of Him that raised up Jesus from the dead dwell in you, he that raised up Christ from the dead shall also quicken your mortal bodies by his Spirit that dwelleth in you.
So we have the Spirit of Christ in us, the Holy Spirit of God who raised up Jesus Christ from the dead in us. The soul, spirit and body are preserved unto perfection until the coming of Jesus Christ for His Body the Church, His Bride.
Where is the only place a lie can be believed? In the mind and that is the only place we can fall to demonic activity. No matter what outside influence may come. We are free and free indeed in Christ Jesus.
Satan cannot possess a born again believer. Because of the Spirit of Christ and the Holy Spirit that dwell in us.
1 Thessalonians 4:8 He therefore that despiseth, despiseth not man, but God, who hath also given unto us His holy Spirit.
1 John 3:9 Whosoever is born of God doth not commit sin; for his seed remaineth in him: and he cannot sin, because he is born of God.
Believing a lie that demon activity can have influence over a bonifide child of God unless God allows it as with Job was, and believing a lie as Adam did.
Colossians 1:27-29 To whom God would make known what is the riches of the glory of this mystery among the Gentiles; which is Christ in you, the hope of glory: Whom we preach, warning every man, and teaching every man in all wisdom; that we may present every man perfect in Christ Jesus: Whereunto I also labour, striving according to his working, which worketh in me mightily.
WE are not in bondage; Acts 7:7 And the nation to whom they shall be in bondage will I judge, said God: and after that shall they come forth, and serve me in this place.
Satan and His nation, an all his angles have already been judged.
In Christ, by His power over me: Phillip