Apologetics is a very powerful tool, but it's ultimately janitorial. Many people encounter obstacles to the faith. Think of the Christian, for example, who loses a relative and is assailed by the question, Why did God allow that? Even the believer can be haunted by difficulties that get in the way of building a relationship with God.
Apologetics can come in and help to make important distinctions and clarify some of the difficulties. You are doing no more than clearing away debris that blocks the door to faith, and ultimately it is God's love that has to work its way into a heart. Conversion ultimately comes from that; apologetics only clears the driveway.
From Dinesh D'Souza in a Christianity Today interview.