Even JP II recognized the Option for the Poor found in both the Old Testament and the New.  The Psalms and all of the literature of the bible constantly maintains that God hears the cry of poor people.  God will defend poor people against the rich.  Nowhere does the Old Testament say that God hears the cry of the rich or protects them in a special way. 

The preferential option for the poor also has strong Christological roots.  Jesus was a victim who was unjustly put to death on the cross.  Jesus identifies with all victims of marginalization, poverty, and injustice.  Jesus came down from heaven and even stripped himself of his divinity  to become one with us.  Jesus chose to be one with the poor and the outcast.  In the scene at the synagogue in Nazareth in Luke's Gospel, Jesus proclaims the good news to poor people and liberation to captives.
---------------------------------------
John Paul II, SOLLICITUDO REI SOCIALIS, 1987