"But if I cast out devils by the Spirit of God, then the kingdom of God is come unto you." (Matthew 12: 28
Here, Jesus rebuked the Pharisees for claiming that He was casting out demons because He was a proxy of Satan.
Such blasphemy would help doom the religious leaders, who rejected the saving grace of Jesus.
In this verse, one of the five in which Matthew refers to the Kingdom of God directly, Jesus specifically mentions the Spirit.
The Holy Spirit brings the Kingdom of God to us.
I submit once again that every time Jesus used the phrase Kingdom of God, He was stressing the offense to religious minds, that the Kingdom cannot be earned, cannot be reached through human efforts.
Furthermore, the Kingdom of God affirms the supremacy of Christ in all things. Even the demons have to bow down and submit to Him.
The phrase "the Kingdom of God is come unto" points out that this Kingdom is not somewhere far away, but is close to us:
"Neither shall they say, Lo here! or, lo there! for, behold, the kingdom of God is within you." (Luke 17: 21)
Jesus shared this truth with the Pharisees, as well.
They receive it, and this gift comes within us.