The Kingdom of God is the rule of God. "The LORD has established his throne in heaven, and his kingdom rules over all" (Psalm 103:19).
Jesus said nothing about what we might call "the politics of the kingdom". He is silent about the geography, organisation and laws of the future kingdom - the consummated or eschatalogical kingdom. Instead His preaching compelled people to repent, to come under the rule of God and so to enter the kingdom now.
When Jesus taught that the kingdom is God "is near" or "has come upon you" He was teaching the coming of the eternal into the temporal - that God is present in a very real and dynamic way and that everyone needs to make a decision: to either come under the rule of God, or to remain in the kingdom of Satan. More than anything else Jesus' teaching demanded that everyone make a decision. Jesus' Gospel of the Kingdom was a message that God has invaded human history and not only has everyone now been called on to come under the rule of God, but they are also enabled by grace to realise a new standard of righteousness. The kingdom is present in a new and unexpected way, and has entered history without transforming history. The righteousness of the reign of God can be experienced in the present evil age, qualitatively if not quantitatively.
Many of Jesus' parables highlighted the radical nature of the Kingdom of God - that it is a totally different from the ethics and standards of the present age. Parables like the workers in the vineyard, the Pharisee and the publican, and others like them show that lives are turned upside down by the ethics of the Kingdom of God. So much of Jesus' teaching was ethical and His ethics are Kingdom ethics - the ethics of the reign of God.
In the person of Jesus we see the embodiment of the ethics of the kingdom. He not only taught how to live under the reign of God, He demonstrated it. Although He is the King, He lived under kingship. So paradoxically He was the Servant-King, as Graeme Kendrick put it in a much-loved hymn. "The Son of Man did not come to be served, but to serve" (Matthew 20:28; Mark 10:45). He taught the Twelve about leadership: "If anyone wants to be first, he must be the very last, and the servant of all" (Mark 9:35). He even brought Himself down to the level of his disciples in identifying with them and said "I no longer call you servants, because a servant does not know his master's business. Instead, I have called you friends, for everything that I learned from my Father I have made known to you" (John 15:15).