This question has been on the minds of many evangelicals in recent years. In considering the question, I found this passage from Michael Horton’s new book, The Gospel Commission, very helpful and insightful:
Pitting Jesus (and the kingdom motif) against Paul (and the emphasis on personal salvation) used to be a hobby of liberal Protestants. Alfred Loissy, a liberal Roman Catholic writer, once quipped that Jesus announced a kingdom, but instead it was a church that came. So on one side is Jesus, with his invitation to humanity to participate in his kingdom by bringing peace and justice, and on the other side is Paul who spoke instead of the church and personal salvation by belonging to it…
Besides revealing a seriously deficient view of Scripture, this contrast between Jesus and Paul rests on a misunderstanding of our Lord’s teaching concerning the kingdom. Jesus’s proclamation of the kingdom is identical to Paul’s proclamation of the gospel of justification. Contracting the kingdom with the church is another way of saying that the main point of Jesus’s commission consists of our social action rather than in the public ministry of the Word and sacrament. In other words, it’s another way of saying that we are building the kingdom rather than receiving it; that the kingdom of God’s redeeming grace is actually a kingdom of our redeeming works.
Jesus’s message of the kingdom as the forgiveness of sins and the dawning of the new creation was inseparable from his promise to build his church and to give his apostles the keys of the kingdom through the ministry of preaching, sacrament, and discipline. This motif of the kingdom was hardly lost in the apostolic era. It was this gospel of the kingdom that Peter and the other apostles proclaimed immediately after Jesus’s ascension (Acts 2:14-36; 3:12-16; 17:2-3). And this aws also the heart of Paul’s message (1 Cor. 15:3-4).
If the preaching of the gospel, no less than the miracles, is the sign that the kingdom has come, Paul’s message and ministry can only serve as confirmation of the kingdom’s arrival.
Michael Horton, The Gospel Commission: Recovering God’s Strategy for Making Disciples, pp. 75-76